West Midlands Police is locked in a battle with documentary-makers over unedited tapes of alleged extremist teachings at a Birmingham mosque.
Channel 4 is insisting it will not hand over the tapes from the Dispatches TV programme without a court order.
Officers have requested the tapes to "establish whether any criminal offences have been committed" at the Green Lane Mosque, in Small Heath.
However, a formal investigation into the teachings of a radical cleric which were revealed in the documentary has not been launched, a police spokeswoman said.
Preacher Abu Usamah At-Thahabi was filmed at the mosque attacking Jews and Christians and calling for homosexuals to be murdered.
Channel 4's Dispatches: Undercover Mosque captured him telling worshippers: "If I were to call homosexuals perverted, dirty, filthy dogs who should be murdered, that's my freedom of speech, isn't it?"
However, At-Thahabi has since defended himself, saying he had nothing to hide and that his words were taken out of context.
Roger Godsiff MP (Lab Sparkbrook and Small Heath) has written to the Chief Constable of West Midlands Police and the Director of Public Prosecutions calling for an investigation into the preachers at the mosque.
He sponsored a Commons motion condemning the "racist and discriminating views" recorded by documentary-makers. A spokeswoman from Channel 4 yesterday said detectives had contacted the broadcaster over the documentary after it was aired last month.
She added: "The police have now requested un-transmitted programme and research material.
"Channel 4's policy, consistent with that of all broadcasters, is to require the police to obtain a court order before such material is handed over.
"The police must satisfy a court that such material is of substantial value to their investigation and that disclosure is in the public interest."
A West Midlands Police spokeswoman said officers were making "preliminary" inquiries into the contents of the documentary.
But a formal investigation would not be launched until officers had information to suggest that a crime had been committed.
The spokeswoman said: "We are concerned about the content of the programme and West Midlands Police are examining the content of the programme."