Channel 4 has been condemned for broadcasting "deeply offensive" language after comedian Frankie Boyle used the words "nigger" and "Paki".
Boyle said the words in an episode of his Tramadol Nights series shown on Tuesday.
Broadcasting watchdog Ofcom is already investigating Boyle's show after he made a controversial joke about Katie Price's disabled son.
Tory MP John Whittingdale said the Scottish comedian should not be allowed to continue with his brand of humour.
"The words nigger and Paki are deeply offensive to a large number of people. I don't think even in comedy it is justified," he said.
"Frankie Boyle is becoming a serial offender. I really think Channel 4 will have to think whether it's appropriate to screen programmes which are regularly causing offence to a lot of people.
"It might be a breach of the Broadcasting Code. Ofcom will have to determine that."
But Channel 4 said the use of the words was "satirical", not racist.
A spokesman said: "Channel 4 strongly refutes any suggestion we are endorsing or condoning racist language by our broadcast of Frankie Boyle's Tramadol Nights.
"This cutting edge comedy is clearly intended to ridicule and satirise the use of these words - Frankie Boyle was not endorsing them.
"Channel 4 would not have broadcast these words had they been used in a racist way. All the jokes highlight the unacceptable nature of this language."
The spokesman added that strong warnings about the content were made ahead of the programme and Channel 4 received one complaint about racism following the broadcast.
A mental health charity said today it had complained to Ofcom about a different sketch in another episode of the series.
Mark Davies, director of communications at Rethink, said the sketch which parodied an advert designed to reduce the stigma around mental illness was misleading and offensive.
The original advert was designed to look like a trailer for a horror film called Schizo but then showed a man, diagnosed with the disorder, talking about he managed to deal with it.
Boyle's version showed a man talking about his problems and the stigma surrounding mental illness, but the camera then panned down to show four dead children covered in blood.
Stuart Baker-Brown, who appeared in the charity's original advert, said: "Stigma and discrimination can be just as harmful as the destructive symptoms of mental illness itself and this sketch can do nothing but cause further harm. It is a shame Frankie Boyle has to act in such an insensitive and unintelligent manner towards those who suffer deeply and towards those who are far less fortunate than himself."
In a letter to Ofcom, Mr Davies wrote: "Rethink fully supports freedom of expression, but we do believe the line must be drawn somewhere. Prejudice and discrimination around mental illness is one of the last taboos in our society and we are determined to do everything we can to tackle it.
"By inferring that people with mental illness are violent, the Frankie Boyle sketch was misleading. One in four people have a mental health problem at some point in their lives. This sketch caused offence to many people in this group."Reuse content