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Claims Sir Keir Starmer's campaign improperly tried to access a Labour membership database are "scurrilous", one of his leading backers has said.

The Information Commissioner is looking into allegations of "data scraping" by staff on the leadership campaign after being alerted by Labour officials.

But MP David Lammy, vice-chair of the campaign, said there was "absolutely no substance" to the allegations.

He suggested whoever was responsible for them was "scraping the barrel".

The report passed to the Information Commissioner surrounds claims that two members of Sir Keir's team sought to obtain information beneficial to the campaign by "scraping" a wider set of data contained in the party's Dialogue membership database.

Mr Lammy said he had spoken to those allegedly involved, including the campaign's compliance official, and he could "categorically" say there was no attempt to mine the database.

"There was no data scraping. It is scurrilous to suggest so," he told Radio 4's Today. "The Information Commissioner must rightly pursue it but I can say categorically this did not happen."

Image copyright Reuters Image caption David Lammy said he hoped the watchdog would conclude its inquiry quickly

Sir Keir's team have suggested the allegations are politically motivated. They point out that they only surfaced after his campaign alerted Labour officials to what they believe was a data protection breach by his rival Rebecca Long-Bailey's campaign.

Her campaign circulated links to volunteers capable of allowing access to the membership database. They say this was done innocently.

Asked whether he was pointing fingers at the Long-Bailey campaign, Mr Lammy replied: "I don't know who has done this or why they have done this but it is very disappointing.

"This is a scramble to the bottom of the barrel. There has been no scraping of data, it feels more about the barrel."

If you accept that public civility and private poison are normal in politics, the Labour Party leadership campaign - which until now has been a tad sedate - has taken a lurch into ghastly normality.

Labour's accusation of hacking of the party's membership database has been met with a flat denial from Sir Keir Starmer's team in public, and behind the scenes, with rage.

Their version of events is that two campaign team members were probing the database for vulnerability to those seeking improper access, as a campaign tool. They were emphatically not, according to the Starmer camp, trying to mine data themselves.

Rather, they say, it was the campaign team of Rebecca Long-Bailey which sent a mass email to volunteers containing a succession of links, a trail of digital breadcrumbs leading to the database doorway.

Her campaign has maintained there was never any intention on its part to lead volunteers into the Labour database.

Labour says it does not have firm evidence of what happened but insists there was a data breach, and it was their duty to report it to the watchdog. There'll be an inquiry into what happened. but whatever the outcome, Labour's leadership campaign has turned very ugly.

The ICO confirmed on Sunday it had received a report of an alleged membership database breach, and would make inquiries.

The watchdog is the UK's independent body set up to uphold information rights and enforce data protection legislation. It potentially has the power to fine any organisation found to have misused data in any way.

Under the party's leadership rules, any candidate who makes it to the final stage of the contest later this month will be entitled to receive details of party membership and registered supporter lists, containing names, telephone numbers and postal addresses.

Sir Keir, Ms Long-Bailey and Lisa Nandy have already qualified after getting sufficient support from trade unions and other bodies affiliated to the party. The fourth candidate, Emily Thornberry, has yet to do so.

It is understood all the eligible candidates are being required to provide guarantees that the information will be stored securely and processed lawfully before it is given to them.

Labour, which is supposed to remain neutral in the leadership campaign, said it had written to Sir Keir and his three leadership rivals to "remind them of their obligations under the law and to seek assurances that membership data will not be misused".

It said it took its legal responsibilities for data protection "extremely seriously."