The cases, disclosed today, include examples of an imam telling viewers that those who disrespect the prophet Mohammed should be killed, and another broadcaster saying homosexuals should be beaten and tortured.
The stations were found to have committed serious breaches of the broadcasting code by allowing the extreme opinions to be aired unchallenged.
Muslim fundamentalists have used British television channels to preach in favour of violent crime and killing “apostates”.
Last night experts warned that the extent and seriousness of the broadcasting breaches raises questions over whether extreme Muslim speakers who were previously confined to small audiences in mosques are able to reach thousands more people by broadcasting intolerant teachings on television.
Although the channels have tiny audiences compared to the mainstream, they are targeted at Muslim communities, including people of Pakistani background, with some of the content being broadcast in Urdu and other languages.
The cases identified by Ofcom include:
* An Islamic scholar who told viewers: “It is your duty ... to kill those who insult Prophet Mohammed.”
* A preacher banned from coming to Britain who used the channel - which he co-owns - to say anyone who left Islam should be put to death.
* A phone-in presenter who advocated “eliminating” anyone who disrespected Mohammed.
In some cases the channels had also breached a rule which states that they must keep recordings of all their output, raising the possibility that other inflammatory material has been broadcast but cannot be traced.
With the exception of one radio broadcaster, the channels ruled against by Ofcom are broadcast on the satellite provider Sky. It has no legal responsibility for what is broadcast on the channels it carries. It is up to the stations themselves to make sure they meet Ofcom’s standards and they can be fined or taken off the air if they do not.
The disclosure of the rulings by the broadcasting regulator comes despite a report in 2010 which warned that extremist material was being broadcast.
Tala Rajab, the researcher who wrote the report for Quilliam, the anti-extremist think-tank, said the fresh findings by Ofcom raised serious questions over the regulation of broadcast material.
“Some of these recent incidents have been quite shocking,” he said.
“If this had happened in a mosque the police would be right in pursuing a criminal investigation. But because they are being broadcast on television channels for some reason there seems to be little appetite for looking into these extreme messages.
“If these kind of comments were made against black people, for example, you can imagine a channel being shut down overnight, particularly if they had incited violence against a minority.”
The 2010 report found that the Islam Channel, Britain’s largest Islamic broadcaster, had continued to ignore Ofcom rules about impartiality and allowed controversial viewpoints to be aired despite a fine and other sanctions being imposed. It is not among the subjects of the five Ofcom rulings disclosed today.
In December a Leeds radio station, Radio Asian Fever, was fined £4,000 for breaching broadcasting rules in programmes involving a presenter called “Sister Ruby Ramadan”.
She told listeners that homosexuals should be beaten and tortured.
“If there are two such persons among you, that do this evil, the shameful act, what do you have to do? Torture them; punish them; beat them and give them mental torture,” said the presenter.
Jabbar Karim, the station’s managing director, said: “We are very embarrassed. This was a one-off incident which will never be repeated.”
Takbeer TV, based in Nottingham, has been found in breach of the code twice in 18 months for programmes which denigrated the minority Ahmadi Muslim sect. Founded in the 19th century its followers are considered by some mainstream Muslims to be misguided or even heretical.
Contributors to the most recent programmes investigated by Ofcom said Ahmadis had a “disease” and “monstrous” intentions.
Ofcom said Takbeer TV had subjected the sect’s followers to “abusive treatment” and that they would now consider an appropriate sanction such as a fine.
An Ofcom spokesman said: “The majority of Islamic channels comply with our rules. However, where we identify issues through our monitoring or complaints we investigate fully and take firm enforcement action.”
He said it was Ofcom’s duty to regulate licence holders rather than the responsibility of carriers such as Sky. However, carriers are free to decide which channels they offer, he added.
A Sky spokesman said: “Sky operates an open and regulated platform. This means any broadcaster with an appropriate Ofcom licence is free to seek distribution over the satellite platform.”
There are 14 Muslim TV free-to-air channels in Britain but their audiences are not measured by BARB, the source of viewing figures.
Takbeer TV failed to respond when asked to comment.