A Channel 4 production team has said it will sue West Midlands Police after the force complained over a documentary about extremism in Birmingham mosques.
The makers of the Undercover Mosque Dispatches programme were reported to Ofcom by the police and the Crown Prosecution Services. But the broadcast watchdog rejected their complaints that the programme had been unfairly edited and distorted preachers' views.
Now Dispatches producers say they will be taking the police and the CPS to court for libel.
A statement by Dispatches editor Kevin Sutcliffe and producers Hardcash Production said: "The statements made by both the West Midlands Police and the CPS were completely unfounded and seriously damaging to our reputation. We feel the only way to set the record straight once and for all is to pursue this matter through a libel action."
Researchers from the programme uncovered extremists preachers at mosques including the Green Lane Mosque, in Small Heath.
A spokesman for Channel 4 defended the producer's actions, saying: "We fully support this libel action as we feel that it is the only way to vindicate their reputations and to prove this was a responsible piece of public interest journalism."
It said it would donate any damages to charity.
A spokesman for West Midlands Police said: "As a result of the concerns raised by Hardcash, the CPS and West Midlands Police are currently in discussions with the programme makers with a view to reaching an appropriate solution."