LABOUR’S attempts to weed out “infiltrators” from its leadership election could be in breach of data protection laws, lawyers warned yesterday.

Candidates Andy Burnham, Yvette Cooper, Jeremy Corbyn and Liz Kendall met acting leader Harriet Harman after Mr Burnham’s campaign raised concerns that thousands of people opposed to Labour remained eligible to vote.

Some members believe they have been targeted specifically for supporting leftwinger Mr Corbyn.

New members, registered supporters and affiliated supporters of Labour are required to state that they support “the aims and values” of the party before they sign up.

Labour has assigned around 70 workers to the task of sifting through new sign-ups to determine their eligibility.

The central party apparatus is also being supplied with intelligence on prospective voters by activists in constituency branches, including data on local political activity and social media postings.

Labour has banned the use of voter data collected by volunteers during doorstep canvassing sessions, but party sources confirmed it had been used for cross-referencing anyway.

Speaking after yesterday’s meeting, held at a secret location in Stevenage, Hertfordshire, Ms Harman said the candidates had had “a useful discussion … a routine discussion, a number of discussions on the process.”

She said they had debated “what further information could be used” in investigations into new members and supporters.

Such inquiries will “carry on right up until the last minute” of the election, she said.

“Whether they don’t support [the aims and values] because they’re Tories or because they’re Trotskyites or because they’re Greens, if you don’t support them, you don’t get a vote,” she said. “It’s not funny or clever.”

She said she was “confident” there would be no legal challenges over the process.

But legal sources told the Star that if the party had used data from canvassing sessions to exclude supporters, it could find itself in “very dodgy” legal territory.

The use of information can be limited to particular purposes — and it is unclear whether data collected for electioneering could be used for membership verification.

“If you give the information to somebody for one purpose, it’s not appropriate for it to be used for another,” one lawyer said.

Another argued that voters could be seen to provide “implied consent” for the use of their data only if they told activists they would vote Labour.

“If they say they’re voting for other parties, there may be a question about data protection,” the source said.

Labour HQ confirmed that it had told party workers to not use canvass data in the process, but acknowledged that in some places it probably was being used.

Former cabinet minister and deputy leadership candidate Ben Bradshaw said last week that his constituency Labour Party in Exeter had cross-referenced new supporters with voter identity data — and found that one in 10 had previously expressed an “extremely hostile” attitude to Labour.

But, speaking to the Star yesterday, he denied activists had been excluded purely on the basis of canvass data.

“This information should be used as a reason to go back and check (the commitment of supporters to the party),” Mr Bradshaw said.

He said he would “urge” the party to allow the use of such intelligence for these purposes — but “absolutely not” as the basis for automatic exclusion.

Asked whether the use of voter data to verify supporters’ commitment to Labour could breach the Data Protection Act, Mr Bradshaw said: “No, that’s wrong, there would be no legal basis at all.

“It’s not being policed or published anywhere … it’s the party that makes these decisions.”

Mr Corbyn, speaking before the meeting with Ms Harman, brushed off concerns about the process, saying it was “great” that new supporters had joined in such large numbers.