Detectives in Bradford were today studying hours of unused footage which was not used in a documentary about the Far-Right British National Party.

And five men arrested in connection with an investigation into the documentary - which showed BNP members confessing to race-hate crimes - have been released, police said last night.

The men were all bailed pending further inquiries by West Yorkshire Police, who are investigating the television documentary The Secret Agent.

The covertly-filmed footage broadcast on BBC1 showed BNP activists confessing to race-hate crimes and party leader Nick Griffin condemning Islam as a "vicious, wicked faith".

On the programme he was seen claiming that he would face seven years in prison if he made the comments in public.

Among those arrested were Bradford BNP councillor Chris Kirby, who represents the Worth Valley, and BNP members Steve Barkham and David Midgley.

A police spokesman said those bailed were a 23-year-old Bradford man, who was arrested in connection with racially aggravated public order offences, a 35-year-old Keighley man, who was arrested in connection with conspiracy to commit damage, and a 51-year-old Bradford man who was arrested in connection with racially aggravated harassment. A man aged 40, from Keighley, was also arrested shortly afterwards in connection with conspiracy to commit criminal damage, followed by a fifth man, a 45-year-old from Bradford, who was arrested in connection with possession of a firearm.

The spokesman said: "Those arrested have been bailed pending further inquiries, to return to a police station at a later date.

"While we need sufficient time to ensure we carry out a thorough and professional investigation into a number of matters, we will bring the inquiry to conclusion as quickly as is practicable.

"A dedicated team of officers continues to pursue numerous lines of inquiry, which includes viewing some material not broadcast.

"Clearly this will take some time but we will issue any significant updates as the inquiry progresses."

In the documentary, which was broadcast last Thursday, a BBC reporter spent six months undercover with the BNP recording another of the group's members, Steve Barkham, confessing to taking part in a racially-motivated attack on an Asian man during the 2001 Bradford riots.

Both Mr Barkham and Dave Midgley, a BNP candidate in the Council elections, have now been expelled from the party.

West Yorkshire Police said last week they would examine footage from the programme.