The London Borough of Barnet has banned 'mother-in-law jokes', once the bedrock of British comedy, because they are offensively sexist and disrespectful to family elders.
In a council publication, staffs are told not to indulge in the gags, which made the careers of classic comics Les Dawson and Bob Monkhouse.
"Humour can be incredibly culture-specific, and is very open to misinterpretation or even offense [sic] by other cultures. And don't forget when you don't know what people are laughing at, it is very easy to imagine that they are laughing at you," the Daily Mail quoted the publication as stating.
"British mother-in-law jokes, as well as offensively sexist in their own right, can also be seen as offensive on the grounds that they disrespect elders or parents," the guide added.
The ban has been greeted with a mixture of anger and bemusement.
Dom Joly, the comedian, broadcaster and author, described the advice as 'completely insane'.
"All comedy is basically about taking the **** out of someone. You either ban it all and end up living in a place like North Korea or you leave well enough alone," Joly said.
Kings of comedy- Les Dawson, Bob Monkhouse and Peter Kay- have all been bastions of the mother-in-law joke
John Sessions, the writer and actor, said the ban was the brainchild of someone with a "sense-of-humour bypass".
"I can almost hear the adenoidal estuary vowels of the person who dreamt up this one," he said.
Barnet uses the 12-page guide in taxpayer-funded equality and diversity sessions for its staff.
It also highlights other cultural differences and potential areas of misunderstanding.
It says the "closed finger and thumb" gesture used by Britons to indicate something is good, is offensive to the French as they use the same gesture to signify worthlessness.
Staff are also told that travellers don't like to bathe in still water and that most Britons would never eat dog or horse, even though they are delicacies elsewhere.
