The BBC has been forced to defend another of its presenter after nearly 200 viewers complained about a remark made by Top Gear host Jeremy Clarkson.
The outspoken motoring journalist was taking part in a lorry-driving task on Sunday night's edition of the show when he joked that lorry drivers kill sex workers.
"Change gear, change gear, check mirror, murder a prostitute, change gear, change gear, murder. That's a lot of effort in a day," the 48-year-old said.
The comments may have been a reference to Steve Wright, a lorry driver jailed in February for the murder of five prostitutes.
The so-called Yorkshire Ripper Peter Sutcliffe, who killed 13 women - many of them prostitutes - was also a truck driver.
Some 188 viewers called the BBC to complain about Clarkson's joke, which was broadcast in the wake of the scandal surrounding Russell Brand and Jonathan Ross' prank phone calls to veteran actor Andrew Sachs.
In a statement, the BBC said: "The vast majority of Top Gear viewers have clear expectations of Jeremy Clarkson's long-established and frequently provocative on-screen persona.
"This particular reference was used to comically exaggerate and make ridiculous an unfair urban myth about the world of lorry driving, and was not intended to cause offence."
However, James Bower, a spokesman for the United Road Transport Union, the body had received "dozens" of complaints from its members.
"We would absolutely condemn what he said about murdering prostitutes. It beggars belief that those words can be broadcast on TV", he added.
"The BBC is an institution that is paid for by the licence fee and they should not be allowing this kind of sick joke."
Media regulator Ofcom confirmed it had been contacted by viewers upset at Clarkson's joke.
"These complaints are currently being assessed against the broadcasting code," a spokesman said.
"All UK broadcasters must adhere to Ofcom's broadcasting code which sets standards for the content of television and radio broadcasting."