The entire membership list of the British National party has been posted on the internet, identifying thousands of people as secret supporters of the far right and exposing many to the risk of dismissal from work, disciplinary action or vilification.

The BNP leader, Nick Griffin, claimed today that he knew the identity of the person who published the list, describing him as a "hardliner" senior employee who left the party last year.

"He didn't like the direction the party was going and broke away, taking the list with him," Griffin told BBC Radio 4's Today programme.

Around 13,500 names and home addresses were posted on a website on Monday evening.

As well as names and addresses, the list includes the home and mobile phone numbers and personal email addresses of BNP members. It is thought the list may include lapsed members of the party and the names and addresses of people who have expressed an interest in joining the party, but have not signed up. Many of the members' occupations are listed, revealing a small number of police, two solicitors, four ministers of religion, at least one doctor and a number of primary and secondary school teachers.

The list was removed from an internet blog today after complaints by the far right group.

A BNP spokesman, Simon Darby, said: "If we find out the name of the person who published this list it will turn out to be one of the most foolish things they have done in their life." Griffin insisted this did not represent a threat of violence but the reality that the person faced prison for breaching a high court injunction. The BNP leader admitted the party was relying on the Human Rights Act, based on EU legislation, which it opposes, to try to protect the privacy of its members.

He said he had no problem with publication of members' occupations but listing their names and addresses represented "a nasty piece of intimidation on behalf of the Labour regime".

However, Griffin welcomed the publicity the story had garnered for the party, saying the list showed the perception of the average BNP member as a "skinhead oik" was "simply not true".

Last night, Darby said the police had been called in to investigate the data security breach. Describing the posting as "malevolent and spiteful", he said: "This isn't a question of us mislaying the information, this is theft."

The BNP list includes the names and ages of children who have become members of the party after a parent has taken out a family membership, and several people who have joined the party at the age of 16.

Against the name of a woman said to be a serving police officer and living on the Wirral, Merseyside, is the note: "Discretion required re employment concerns - police officer", along with the names and ages of a number of her children.

Other notes against the names of individuals include: "Discretion requested (employment concerns), government employee, IT consultant" and "activist (discretion requested), teacher (secondary school)".

The BNP is known to go to considerable lengths to conceal the identities of members. Membership lists are held on computer spreadsheets, usually by an official based in York. He sends limited lists to local organisers as encrypted attachments to emails that can be accessed only by officials who have been given a password.

The BNP conceded that very few people would have had access to its full membership list. The party said the list was not up to date, featuring no members who had signed up since late 2007, and included the names of people who had never been members of the party. The party said it had obtained an injunction this year at the high court in Manchester to prevent the misuse of its membership list.

Griffin confirmed on the party's website that much of the list was genuine, and that it contained data stored at some point between November 30 and December 2 2007. "This latest attack is not really directed against our own people, who are already tough-minded and know that nothing ever comes of this sort of bluster, so much as against the thousands of [members of the UK Independence party] who are thinking of joining us.

"It probably will frighten some of them, but it's water off a duck's back to the stout hearts of the British National party."

Last night, internet chat rooms frequented by British supporters of the far right were buzzing with anger, indignation and considerable alarm. One typical posting said: "The most shocking thing is some of the comments by the names! God help anyone who is in the army, the prison service, health care, a police officer or a teacher."

It is thought the information commissioner, who enforces the Data Protection Act, may investigate the matter, looking not only at the posting of the list but at the amount of information the BNP has been storing about its members.

A spokesperson for the Information Commissioner's Office said: "Following media reports that the personal details of BNP members have been incorrectly disclosed, we will be contacting the party to establish the full facts. We will then decide what action, if any, is appropriate.

"We encourage all organisations to alert the Information Commissioner's Office if they discover a security breach has occurred."

The membership list reveals that the BNP has a handful of members in Australia, one in Oman and around 17 living in the United States. Some of the members' hobbies are listed. One gives her occupation as "holistic therapist" and her pastimes as "metaphysics, cartoon drawing". Another lists his hobbies as "fantail doves, koi carp, gardening".

There are one or two insights into reasons that people have left the party. Against the name of one lapsed member from Gillingham, Kent, is the note: "Objects to being told he shouldn't wear a bomber jacket."

• Additional reporting Duncan Campbell and Paul Lewis

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