NICK GRIFFIN is to be investigated by the privacy watchdog after the BNP leader was accused of paying for a database containing the names and addresses of thousands of members of a rival party.

The database, which belonged to the UK Independence party and contained the details of about 3,500 of its members from London and the southeast, was passed to the British National party by a disaffected member in return for about £500, sources say.

The BNP then canvassed many of the people on the UKIP list asking for funds to help fight its campaign in the run-up to June’s European elections. The BNP went on to claim two seats, including one for Griffin.

Last night the Information Commissioner’s Office (ICO), which oversees data protection, said it would investigate. Under the terms of the Data Protection Act, anyone who sells data without authorisation from the designated “data controller” is guilty of an offence, as is the person who obtains it.

If prosecuted and found guilty, transgressors are liable to a fine of up to £5,000. The Ministry of Justice is consulting about whether to impose custodial sentences for future breaches.

Griffin said yesterday that he had never personally paid for a UKIP membership list, although he conceded that some UKIP details had been passed to his party by former members.

He added: “To the best of my knowledge, no one in the party has paid for such a list.

“Some UKIP members do join us and provide names and addresses of people who might be interested to hear from us. We have never had an entire UKIP membership list.”

Last week Griffin said the anonymous leaking on a website of his own party’s membership — the second time it has happened in the past 12 months — was part of a “concerted anti-BNP campaign”.

One of the names on the leaked UKIP database was Gerard Batten, an MEP for the party, who has previously complained to the ICO about the apparent data breach. Last night he said he was preparing a fresh complaint based on The Sunday Times’s evidence that the database had been bought and sold.

“We have long suspected the BNP had a [UKIP] membership list. Our members don’t want this stuff. The BNP do this based on the false belief they can take away some of our members,” he said.

Batten and others received unsolicited requests for donations from the BNP from 2008 until earlier this year. One sent in January appealed for funds for the BNP’s European election battle. It said: “If we can win one seat, the floodgates will open. One seat, just one, would put us on the world stage and would lead to an avalanche of popular support throughout this country.”

Last year Batten wrote to the ICO: “I suspect that my address and those of our UKIP London members were illegally accessed from a UKIP database.”

Now other sources, including from within the BNP, have confirmed that the database was obtained and exploited by the party. “Nick Griffin bought the database for surprisingly little, just a few hundred pounds,” said a source.

It is understood that the privacy watchdog wrote to the BNP warning it not to send Batten any more communications. But the source said the watchdog did not know the party also had the names and addresses of 3,500 other UKIP members.

An ICO spokesman said: “We are very concerned to hear that some UKIP members’ personal details have apparently been traded with the BNP. We will investigate this incident to establish the full facts.

“Buying or selling personal data is against the law, unless there is a public interest defence.”

Gerry Gable, publisher of the anti-fascist magazine Searchlight, said: “The BNP jump up and down when their own membership lists are leaked, but it now emerges they are procuring the details of members of another party in an underhand way.”

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