KEIR Starmer's leadership campaign has said it is "scurrilous" to suggest it breached data rules after Labour reported allegations that it had done so to the Information Commissioner’s Office.

The suggestion is that the Shadow Brexit Secretary's team hacked into the party's membership database to gain an advantage. But supporters of Sir Keir suspect the Corbynite wing of the party is using dirty tricks to disrupt his bid for the Labour crown.

However, the campaign team of Sir Keir’s main rival, Rebecca Long-Bailey, forcefully rejected any suggestion it was behind the decision by Labour officials to refer the London MP to the ICO, which was then leaked to the media.

A spokesperson for the Long-Bailey campaign said: “The investigation into Keir Starmer’s campaign over an alleged data breach should not be allowed to distract from a moment of significant importance in determining the future direction of our party.”

Later, Matt Zarb-Cousin, Ms Long-Bailey’s communication director, denied claims he or Jon Lansman, her campaign chief, had leaked the news, insisting the campaign was “totally clean”.

Sir Keir is seen as the frontrunner to succeed Jeremy Corbyn but the allegation now threatens to damage his prospects and drag the contest into bitter recriminations.

His campaign vice-chairman, Labour backbencher David Lammy, said there was "no substance at all" to the allegations.

"It didn't happen. There was no data-scraping. I can say categorically that this did not happen and it's denied fundamentally," declared the Tottenham MP.

"There was no attempt by the campaign to do this; it's scurrilous to suggest so and I'm quite sure that the Information Commissioner will find the allegations completely untrue," he added.

The allegation came as Labour also investigated a complaint about Ms Long-Bailey's use of party data.

Mr Lammy did not link the allegations but described the report to the ICO, which was set up as an independent body to safeguard information rights, as "disappointing".

"I hope this isn't now a scramble to the bottom of the barrel because there's not been any scraping of data, it feels more about the barrel really," said the backbencher.

Labour was understood to have been conducting a "thorough investigation" into the claims against Sir Keir's team.

And Jennie Formby, the party’s General Secretary, wrote to all candidates following the reports about alleged misuse of membership data and party systems.

A Labour spokesman said: "The party takes its legal responsibilities for data protection and the security and integrity of its data and systems, extremely seriously.

"We have written to all leadership candidates to remind them of their obligations under the law and to seek assurances that membership data will not be misused."

Candidates are preparing for the Scottish hustings, which take place in Glasgow on Saturday.

Mr Corbyn's successor will be announced at a special conference in London on April 4.