A councillor's suggestion a local authority could “boycott” a city taxi firm over an advert attacking 20mph speed limits has sparked a political storm.

Green councillor Ben Duncan asked whether Brighton and Hove City Council should sever links with cab company City Cabs over the anonymous paid-for piece published on Wednesday last week.

The advert in The Argus suggested a “crippling” move by council bosses to force city-wide 20mph speed limits was a “declaration of war on motorists”.

A second advert published in The Argus on Saturday said: “Driving around Brighton and Hove is tough enough. We don’t want it to become any harder.”

Councillor Duncan said the first advert was “based on utter mistruths” and claimed it had been produced by furious taxi bosses determined to derail the controversial policy.

On Twitter he said: “Wondering if we’ll have to start urging official BHCC boycott of City Cars (sic) after they declare war on council 20mph speed limits.”

Some delegates at the Green Party Conference were quick to support the idea, with one tweeting: “Boycott City cabs / Southern Taxis who paid 4 Brighton Argus anti 20mph ad.”

Councillors gave the go-ahead on the first phase of the 20mph proposal in January, claiming the move will improve road safety and air quality.

But taxi firms have long opposed the plans, insisting slower speed limits would lead to frustrated passengers attacking drivers.

Speaking yesterday, Councillor Duncan said he “strongly disagreed” with a boycott but said it was important to debate the idea.

He said: “I think a boycott at this point would be disproportionate – and it’s important that we know all the facts first.

“I can see why a child or someone with subnormal intelligence might assume I was calling for a boycott now but they’d be wrong.

“The problem is that this ad was based on untruths. It suggested that the 20mph limit was a war on motorists, when in fact it is about enforced peace.”

But opposition councillors disagreed, with some accusing Coun Duncan of attacking hardworking taxi drivers in order to make a political point.

Councillor Warren Morgan, leader of the Labour group, said: “I'm very concerned at this irresponsible call for a boycott of local taxi drivers, who work long hours in order to make a living.

“The Greens can't keep saying whatever they like regardless of the consequences.”

Conservative councillor Geoffrey Theobald said: “I think it’s outrageous in a democracy taxi drivers have every right to express their views.

“Nothing ceases to amaze me in the way in which Green party members are expressing their views about people who don’t agree with them.”

Labour peer and former council leader Steve Bassam tweeted: “BHGreen Party now want BHCC to ban use of City Cars (sic) because they had the temerity to question how 20mph is being introduced.

“There is nasty authoritarian streak to BHGreen Party now calling for council boycott of City Cabs & Southern Taxis over 20 mph plans.”

This morning, Green council leader Jason Kitcat said: "Just to be very clear - there is no Green Party nor Green administration sanctioned boycott of taxis."

And fellow Green councillor Sven Rufus said: "Don't assume what Ben Duncan says is GP policy. No boycott. Disappointed by ad though."

The Argus understands a complaint has been made about the first advert to the Advertising Standards Authority.

Last night taxi bosses declined to comment.