But centrists said the allegation was “pumped up” in an attempt to derail the shadow Brexit Secretary’s campaign in favour of Corbynista candidate Rebecca Long-Bailey. The row came as Sir Keir was hit by a family tragedy after his mother-in-law died following an accident. Labour said it is conducting “a thorough investigation” into the hacking claims and has written to all candidates warning them not to misuse data.
Sir Keir’s team said the allegations were “nonsensical” and only surfaced after they had raised concerns last week about a potentially “very serious” data protection breach by rival Ms Long-Bailey’s team.
Lord Falconer, a Cabinet minister under Tony Blair, said the decision to report Sir Keir’s campaign, then leak the story “tells us much more about the sense of the left in labour losing its grip on the party”.
“Do you believe Kier Starmer or do you believe that shower that have been around dealing for example with allegations of anti-Semitism? My money is on the Kier Starmer side, not on that lot, we know they can’t be trusted,” he told BBC Radio 5 Live Pienaar’s Politics.
“It’s a pumped up allegation given to the media straight away rather than in any attempt to investigate the truth it really honestly makes me think, as a long term labour member, that we really need to be able to make sure that you can trust the organisation of the Labour party.”
Jenny Chapman, who is running Sir Keir’s campaign said the allegations are “utter, utter nonsense” and “didn’t happen”.
She said the contest is “supposed to be a clean fight” and the actions are not “doing the Labour party or their preferred candidate any favours here”.
The Information Commissioner’s Office (ICO), an independent body set up to uphold data rights, confirmed it had received a report of a membership database breach and said it would make inquiries.
Sir Keir has raced ahead in the contest, winning widespread support among MPs and local parties as well as crucial union backing.
Ms Long-Bailey has made it through to the final ballot but her campaign has been viewed as lacklustre.
A Labour spokesman said party takes its legal responsibilities for data protection “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,” he added.