As Government whip with responsibility for foreign affairs, my job gives me some insight into how hard Tony Blair and Jack Straw have been working.

They want to find a peaceful solution to the Iraq crisis.

I know the Prime Minister does not want military conflict. Neither do I. But I know, too, he believes allowing Saddam to retain his weapons of mass destruction will lead not to peace but much more conflict and bloodshed in the end.

This is why he has tirelessly tried to win support for a second UN resolution to make clear to Saddam that he must rid himself of his chemical and biological weapons and end his ambitions to develop nuclear weapons.

After all, this is only what the UN demanded of Saddam - and what he promised to do - 12 years ago at the end of the Gulf War.

The UN made these demands because Saddam is a uniquely brutal and reckless dictator. A dictator that has used weapons of mass destruction against his own people and his neighbours, invaded two countries and fired missiles at five.

A dictator, too, who has killed, tortured and imprisoned hundreds of thousands of Iraqis and driven four million into exile.

Over the last few weeks, Tony Blair has been ready to listen, to compromise and to negotiate to build an international consensus to send a tough message to Saddam that he must finally disarm or be disarmed.

He believes - as I do - that a strong united stance by the UN is the best chance of a peaceful solution by persuading the Iraqi dictator that he had no choice but to meet his international obligations.

Let's not forget that it's only the credible threat of force which persuaded Saddam to allow the UN weapons inspectors back into Iraq last year.

Even at the 11th hour, Britain has laid down six tests by which Saddam could prove he was serious about disarmament.

These tests include, for example, demands that Saddam surrenders the 10,000 litres of deadly anthrax the inspectors say is still missing or produces the evidence to prove it has been destroyed.

But UK hopes of building UN support has been made much more difficult by the extraordinary stance of Jacques Chirac.

The French President rejected the new proposals without discussion. Rejected them, in fact, even before Saddam did.

And it shows the French are deadly serious about their threat to veto any second resolution 'in whatever circumstances'.

It's a threat which has undermined hopes of building any united UN position. And one difficult to reconcile with the Security Council Resolution 1441 - which France and every other member supported last year - that Saddam had a 'final opportunity' to meet his disarmament obligations or face 'serious consequences'.

It has also, I am convinced, sent a message to the Iraqi dictator that the tactics of deceit, delay and division, which he has used for 12 years, are working so he does not need to disarm.

I'm not sure why the French President has taken this position. All I know is that it has made military conflict more, not less, likely.

And it is all the more unreasonable because of new and damning evidence the chief weapons inspector Hans Blix produced this month about Iraq's weapons of mass destruction.

His 173-page report itemised huge stockpiles of still missing weapons including 550 mustard gas bombs, 6,500 chemical weapons bombs, material for Sarin and VX nerve gas and 10,000 litres of anthrax.

If we now fail to uphold the authority of the UN laid down in Resolution 1441 and allow Saddam to continue building up his deadly weapons arsenal, then he will come out of this stronger and more dangerous and the UN weaker.

It will tell other rogue countries that the UN is not serious about the spread of weapons of mass destruction.

And it will increase the chances of terrorists getting their hands on these weapons and using them in a catastrophic attack. This is our real nightmare.

These are the reasons that Tony Blair is taking such a strong line on Iraq. He's doing it because he believes it is in Britain's national interest to ensure Saddam is disarmed and the UN's credibility is maintained. And it is why he has my full support.

Ivor Caplin is the Labour MP for Hove