Most of us are content with doing our recycling and taking the odd bus instead of the car but Dr Caroline Lucas MEP has dedicated her life to changing the world for the better. One of only two British Green Party Members of the European Parliament, she is now ready to take on Westminster.

SARAH LEWIS talks to her.

It can be quite hard following what Dr Caroline Lucas MEP is saying because she doesn't actually speak in sentences. It is more a constant stream of words - ideas and opinions - out of which, even if the intention of the question was personal, the answer invariably emerges as political.

But if politics is theatre for the ugly, Caroline does not look like a politician.

She is gently stylish with sharp features and a bright demeanour, a far cry from the dull, middle-aged fat men we have come to accept as our public servants.

She is also shy and quiet, surprisingly so, since on paper she sounds appreciably more rowdy. Known for crying antiestablishment at massive rallies which fill Trafalgar Square, her website proudly displays a photograph of four policemen carting her off, one carrying each limb, after a protest outside Faslane Naval Base in Scotland, a storage facility for Trident nuclear weapons.

Last week, she was controversially selected over long-standing councillor Keith Taylor to stand for Parliament for the Green Party in Brighton Pavilion at the next general election and, last month, she caused uproar when she criticised the media's treatment of climate change, comparing the behaviour of sceptics to holocaust deniers.

In 2006, Caroline, who is only 37, was voted in the top ten of the New Statesman's Person of the Year awards.

This year has seen her voted Politician of the Year in the Observer newspaper's Ethical Awards, beating David Cameron and Gordon Brown to the title, and come eighth in New Consumer magazine's Ethical Top 100. New Consumer commented: "If you had to trust one person with changing the world you could do worse than rely on Lucas".

We meet near Seven Dials in Brighton in the house of fellow Green Party member Simon Williams. She is over in the UK briefly from Brussels, where she currently lives with her husband and two children, although a win for the Greens in Pavilion will see a hasty move to Brighton. I have managed to claim half an hour of her oversubscribed time.

She perches nervously on the edge of a wooden chair and tells me the trip to London is easy, thanks to Eurostar, but between London and Strasbourg is much less so: "I do sometimes fly and I hate doing that - but it's just how you juggle the different pressures of the job."

For Caroline, her lifelong campaign to save the world from itself began in the Eighties. She was studying for her PhD in English literature in London in 1986 when she happened upon Jonathon Porritt's environmental manifesto, Seeing Green.

"How I got from there to here was that very simple event," she says. "I remember being utterly inspired by it.

I noticed as I closed the book that the Green Party office was on Clapham High Road. By chance I was living in Clapham at that point so I thought, Right! I'm going there now, I'm just going to dedicate the rest of my life to this party'.

"So I marched up and down the Clapham High Road looking for what I imagined would be this enormous office. Eventually, I tripped over this tiny room behind a Chinese restaurant and laundry, and there was one woman behind a computer - not even a computer - a typewriter, and a small baby on the floor and I said, I'm looking for the Green Party'. She said, Oh, you've found us'. I joined up there and then."

At that time Caroline was also involved with the Campaign for Nuclear Disarmament. Inspired by the women at Greenham Common, she took part in the Snowball Campaign, a countrywide movement against nuclear weapons which saw growing numbers of people cutting fences at various military bases with the aim of getting arrested.

"The idea was you had so many people doing it, the courts wouldn't be able to process everyone and, hopefully, it would prompt a rethink of nuclear weapons.

Sadly, it didn't get to that level. I did get arrested but eventually they dropped the charges, which was a bit disappointing."

The disappointment was redressed last year when she was arrested again, this time at Faslane, and this time she was charged. She is surprisingly happy about it and explains her belief in nonviolent direct action if the democratic avenues don't work. For Caroline, Trident is a case where democracy has failed miserably. "I strongly believe the Government's decision to update and renew its Trident missile system is against international law," she says.

"There is the nuclear non-proliferation treaty which says very clearly those states which acquired nuclear weapons should progressively disarm and those states that don't have them should pledge not to have them.

"We seem very good at trying to police the second one, for example with Iran, yet somehow don't seem to see the complete hypocrisy of at the same time getting more nuclear weapons ourselves."

She defended herself in court on this basis after being charged with breach of the peace. She laughs: "Unsuccessfully, because I still got done for it."

The massive irony, she points out, is that sitting down quietly outside the nuclear base was somehow breaching the peace, rather than the nuclear base itself - "this horrible thing that has the capacity to destroy the world".

After joining the Green Party, Caroline took a journalism correspondence course, becoming the party press officer.

"They were offering such a pittance no real press officer in their right mind would apply for the job," she says.

Her time in that job was a seminal period for the party. In 1987 they won only 0.3 per cent of the general election vote yet by 1989 they found themselves with a staggering 15 per cent in the European elections.

"I'm not claiming credit for that but it was an extraordinary time and there was so much belief then that we were going to break through," she says. "We really thought 15 per cent was going to change British politics forever."

British politics did not change forever, however, and a shocked and unprepared Green Party let support fall away and votes were lost to the newly emerging Liberal Democrats.

Four years after their success in Europe, and with a new approach to win back public support, Caroline won a seat on Oxfordshire County Council, only the second seat ever won by a Green. Five years later, in 1999, when a system of proportional representation was introduced, she was elected as a Member of the European Parliament.

She says: "You began to get this pattern where you had a voting system in which you could go to people and say if you vote Green, you get Green."

The flurry of activity in her professional life was also matched in her personal one. She married husband Richard in 1991 and in 1993, the same year she won her Oxfordshire seat, had her first child Theo, now 14. Isaac, now 11, came three years later in 1996.

"My memory of being elected to the county council is very funny. My eldest child at the time was only three months old and was still being breastfed.

Looking back at the coverage you can see me beaming, with my green rosette and everyone saying well done, but if you look really carefully at the back you can see Richard walking backwards and forwards with a crying baby desperate for a feed."

It was joked the reason she won that election was because voters found it hard to slam the door in the face of a doorstepping politician with a baby in a sling.

"I worry about the children enormously because obviously I'm not as present as I'd like to be," she says. "I do think both I and they are making big sacrifices, but at least I'm choosing it.

The way I explain it to myself when I am away more than I want is that the reason I'm doing it is to ensure there is a habitable planet in the future."

Caroline's recent selection in Pav ilion was a close-run thing, winning 55 to 45 per cent of the vote. A lucky margin since Caroline declared she did not want to cause any internal rifts and would not stand unless she won by at least ten per cent.

The party's internal politics are a touchy subject, though. The Greens like to set themselves apart from the other parties by presenting a united front without any of that petty pointscoring all the others seem to go in for.

Although rumours of infighting have been trickling into the mainstream, they have, until now, been quite good at keeping it under wraps.

Caroline cannot contain a smirk and looks bashfully at her lap when I ask her how she would differ as an MP from Taylor. "It just gets us into very controversial waters," she says.

"We both have very different skills, Keith is a real local politician. One has to hand it to him, he's done a fantastic job here and he's very well known and he's built up a very strong local presence.

"I suppose I would argue that for the very first Green MP we have to have somebody who is very experienced at a national level."

He is much less coy about matters when, just two days after I speak to Caroline, he unexpectedly launches a searing public attack on her, claiming her comparison of climate change sceptics to holocaust deniers showed a serious lack of judgement.

"It was a strong thing to say," she says, "and I didn't do it lightly because I know what sensitive ground one is treading on, saying something like that. In a sense the reason I did it was to try to wake people up a little more.

"You know, I am literally awake at night thinking about the fact some of the best scientists in the world are telling us we have between eight and ten years to put in place the policy framework we need.

"I honestly believe we are sleepwalking towards a major catastrophe, it just seems quite extraordinary people are getting on with their everyday lives when there really could be such a catastrophe round the corner."

Ultimately, the comment was born of frustration. Time and time again she has been asked to debate the matter with prominent climate change sceptics such as Bjorn Lomburg or Richard North. She says: "It's just such a waste of time because they really represent such a tiny minority of people.

"We ought to be having a debate about how we do it, when we do it - the exact details."

For all Caroline's plaudits, the holocaust comment is just one of an increasing number of moves which have earned criticism from the public.

Others are what some people see as her open support for Hamas or her distaste for things most of us see as progressive and, well, normal, such as globalisation or free trade.

Yet even though she looks demure and harmless right now, the feeling she actively seeks those eyebrow-raising moments is unmistakable.

In an email to the Green Party responding to the uproar surrounding her holocaust comments she says: "There are other unpalatable truths we need to have the courage to talk about as well - population is a key one.

Why does no one, in the discussions on climate change, talk about the need to think about a future reduction in human numbers?"

They are brave waters to be wading into, indeed, but she does have a politician's knack for making all these things add up.

"I'd stress what I don't like about globalisation is the economic side,"

she says. "The one-size-fits-all imposed on every part of the world - as opposed to globalisation in terms of technology and communications, all of which, of course, I support."

She goes on to explain the aspects she doesn't like are those which mean trade and competition only ever grow bigger. After all, how is an everincreasing demand for "stuff"

compatible with oil running out and dwindling resources?

"When you consider about 50 per cent of all international trade basically involves the simultaneous export and import of more or less the same product, it does seem bizarre there is just so much needless trade going on."

Even the argument that developing countries need our business to help them grow does not assuage her.

"Actually, there's an argument that free trade hasn't benefited the poorest.

If you look at the UN reports they're saying the past 20 years - the time of the fastest pace of globalisation - has actually seen some of the poorest countries getting even poorer as, for example, in some countries their agriculture becomes solely about exporting, which means the poorest people don't have any land left for any kind of subsistence farming at all."

She finishes emphatically: "The model of economic globalisation does not help the poor, broadly speaking, and it certainly does not help the environment."

I comment on an acquaintance who persistently insists climate change is fantasy. She looks up for the first time and laughs openly, a hint of what real-life Caroline might be like. She swipes her hand as though giving the air a thick-ear and growls "Send 'em round!"

Her philosophy on dealing with such people is this: generally, people won't say climate change isn't happening, they'll say we don't know it is happening. In which case, if we take the scenario it is not happening and we don't do anything, the impact of that - if it is wrong - is the deaths of millions of people and possibly the end of the planet as we know it.

"So that is a pretty big risk,"

she says.

If the people who do believe climate change is happening are wrong it is not so much of a problem. We will have better public transport, a better energy policy, more efficient systems and be less dependent on unstable parts of the for our fossil fuel.

Caroline says: "Even if the deniers are right, I think there are so many good reasons for taking this path."

It would be easy to mistake Caroline for someone with an intensely negative view of the world but, despite everything she sees as wrong, there is a surprising pragmatism and inherent optimism about her.

"Climate change is just a symptom of the way in which human beings have got out of balance with the planet," she says. "Over the past 30 years we have more or less doubled our GDP but our satisfaction levels have not followed suit.

"According to a set of indicators such as substance abuse or mental illness or suicide they have actually got a lot worse. So we've got an economic model that isn't delivering wellbeing and at the same time we've got climate change which requires us to change our economic system.

"Now, the idea we could actually put these two things together and say well let's change the economic system in order to deal with climate change in such a way that is actually going to fulfil our wellbeing so much better - that, to me, is a fantastically optimistic vision of the future."

We finish the interview, I pick up my bag and prepare for some goodbye chitchat but she has already left for the living room and is lost in conversation with other Green Party members.

Saving the world is one thing, but idle chatter, I should have realised, is probably not something Caroline does.