Smash hit

Nick Griffin, the BNP leader, initially accused former BNP staff members who have been sacked, telling the Today programme on BBC Radio 4: "We are pretty sure [that we know who leaked it].

"We had a problem with a very senior former employee who left last year. He was one of the hardliners I inherited from my predecessor, he didn't like the direction the party was going in, thought it was too moderate, so he broke away taking the list with him."

The BNP won a High Court injunction against a former member in April preventing a membership list being made public.

WIthin a couple of hours, however, the BNP appeared to be backing off from accusing its former employee, and turning its sights on the Labour Party.

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"It is looking increasingly likely that this is the work of Labour Party supporters," said Simon Darby, the party spokesman. "If they have not protected their IP [internet service provider address] properly, there will be an electronic trail leading back to the culprit."

Jacqui Smith, the Home Secretary, showed little sympathy over the leak. She told Sky News: "It probably says something about the BNP that people don't want to have it known that they are a member."

Mr Griffin was forced to deny that Mr Darby had intended to threaten violence when he said last night that if the culprit was found, "it will turn out to be one of the most foolish things they have done in their life", and that "I wouldn't be sleeping very well tonight".

Mr Griffin told Today: "There is no threat of violence as is being reported today."

Others whose names, jobs and contact details are posted online were this morning in fear of their jobs, as the names include prison officers, who in 2002 were also explicitly banned by their employers from holding BNP membership.

Teachers, doctors and serving members of the Armed Forces are among the members listed, and now face questioning from colleagues and bosses over whether belonging to a party associated with racist views is compatible with the caring ethos and emphasis on equality in their work.

The BNP said in a statement on its website that it had lodged a complaint with Dyfed-Powys Police on the grounds that the "disgraceful act of treachery" breached human rights and data protection law.

Mr Griffin admitted that the Human Rights Act was one of the BNP's pet hates, but denied that using it to enforce the privacy of its members was hypocrisy.

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