The man who helped expose the Far-Right British National Party in Bradford urged people not to be taken in by its new image of respectability.

Speaking after the TV programme "From Boots to Suits" shown last night on television, Andy Sykes said: "It highlights yet again what the BNP are - thugs and race haters."

The programme showed how the BNP was trying to change its image and become more respectable to gain votes.

Mr Sykes, 36, himself was involved in a television programme - The Secret Agent - where he helped a BBC reporter go undercover exposing the allegedly criminal side of the BNP in Bradford and Keighley. BNP activists were shown discussing firebombing vehicles, bombing mosques and shooting Muslims.

Four men from Bradford and two from Keighley were arrested last month after police launched an investigation following the programme.

Mr Sykes said: "A leopard does not change its spots. They pretend to be respectable while harbouring hard-line Nazi views as this programme clearly showed."

The programme showed Bradford councillor Dr James Lewthwaite (BNP, Wyke) urging a party meeting to start changing the type of people it selected as BNP candidates.

He said the tattoos had to go and if they elected the right representatives they would start to represent the suburban estates.

"We have to get quality candidates in the right sort of wards," he said. "We do not want knuckle scrapers, piercings and baseball bats. Anything like that will not win votes."

Mr Sykes praised author Nick Ryan who had been researching the group for five years and who agreed to shed his anonymity for the programme to expose his findings.

Mr Sykes, who spoke exclusively to the Telegraph & Argus about his undercover role and has since had death threats, said: "I do not know Nick Ryan but he is a brave man."

The programme concentrated on BNP organiser Nick Cass from the Dewsbury area and showed undercover footage at a Cleckheaton meeting.

Paul Meszaros, of Bradford TUC, said the programme had shown the grass-roots party in action. "I think it showed clearly what they are about. That thin veneer they present drops so readily," he said.

Meanwhile, Keighley MP Ann Cryer said she believed there could be a positive outcome following the screening of the controversial Channel 4 programme Edge of the City also screened on Channel 4 last night. She said there had already been major improvements in Keighley since it had been completed.

The documentary revealed how predominantly Asian groups of men were grooming young girls for sex. It featured two mothers whose daughters had been lured into relationships by the men.

The programme had been pulled from the schedules before June's local Government elections on the advice of West Yorkshire Police for fear it could incite racial hatred.

"We've learned a lot," said Mrs Cryer. "I didn't know what was happening under my nose until the mothers told us. It's a whole new ballgame now. We know what's going on. One of the most positive outcomes is in schools."