Comedian Steve Coogan has attacked the three presenters of BBC1's Top Gear as unfunny "uber-conservatives" whose attempts at humour are more tragic than comic.

In a strongly worded onslaught on Jeremy Clarkson, Richard Hammond and James May, Coogan said that the trio's recent derogatory comments about Mexicans were misjudged, ignorant and typical.

Writing in the Observer this weekend, Coogan accuses Hammond of acting as a sycophantic sidekick to the programme's chief bully, Clarkson. May does not escape scorn either. According to Coogan, he is guilty of effectively holding the coats of his two co-presenters while "they beat up the boy with the stutter".

Hammond's remark last week that "Mexican cars are just going to be lazy, feckless, flatulent, overweight, leaning against a fence asleep looking at a cactus," provoked a storm of criticism. Complaints from viewers began to flood in when Clarkson added to Hammond's insult by joking that the Mexican ambassador would be sleeping in front of the television so wouldn't be able to muster a protest.

But the ambassador, Eduardo Medina-Mora Icaza, was in fact listening and has asked for an apology.

Since then a Mexican woman living in London has decided to bring a test case against Top Gear.

Jewellery design student Iris de la Torre is to make a claim against the BBC under a new equality law. Her lawyers have demanded the hit BBC2 motoring show is taken off the air and that there is a formal investigation into the incident.

Clarkson is undeterred. In his column in the Sun yesterday he complained that "there are calls in Britain at the moment for all offensive humour to be banned. But what people don't realise is that without offence, there can be no jokes."

Indeed, far from apologising, the presenter finished his article with another deliberately tasteless joke: "Mexico doesn't have an Olympic team... because anyone who can run, jump or swim is already across the border."

Coogan, who says he is a "huge fan" of Top Gear and has appeared on the show three times, argues that "The Lads" have misguidedly adopted an air of anti-establishment "coolness" that ends up being as "lazy, feckless and flatulent" as their Mexican stereotype.

The point of comedy, Coogan claims, is to prick pomposity and not to pick on the weak. "It's true there are no hard fast rules; it's often down to judgment calls. It's safe to say though, that you can get away with saying unsayable things if it's done with some sense of culpability," he explains.

"If I say anything remotely racist or sexist as Alan Partridge, for example, the joke is abundantly clear. We are laughing at a lack of judgment and ignorance. With Top Gear it is three rich, middle-aged men laughing at poor Mexicans."

The star of television comedies such as The Trip, Saxondale and The Day Today is critical of the BBC too.

The corporations's initial "pitiful" apology was "mealy-mouthed" he says, adding that the comments made on Top Gear are important because the programme has such a high international profile.