Sir Keir Starmer has declined to identify all of his donors, after coming under pressure to disclose who is funding his Labour leadership campaign.
The frontrunner in the race to succeed Jeremy Corbyn insisted on Wednesday that he was sticking by party rules on finances, but his rivals say they have gone further.
Rebecca Long-Bailey and her allies have called for greater transparency from Sir Keir, with shadow minister Jon Trickett suggesting the delays were “anti-democratic”.
Shadow Brexit secretary Sir Keir criticised “this line of attack” when repeatedly pressed to reveal all of his donors during an interview for The Andrew Neil Show on the BBC.
“How can you say I’m hiding behind process when it’s the Labour party process,” Sir Keir said, when pressed on who his five biggest donors are.
“I’ve got a compliance team in place who are checking every donation is in accordance with the rules,” he said.
“Once they’ve done that they pass it to the Parliamentary authorities for them to publish it. So two lots have gone up, another lot is with the Parliamentary authorities as of today, I’m following the rules.”
While not saying who his biggest donors are, he did, however, say that the biggest donation he has received was £100,000 from fellow lawyer Robert Latham, which was published on Parliament’s register of interests on Tuesday.
Asked if she thinks Sir Keir is hiding something, Ms Long-Bailey said that “I hope not”.
“But I think it’s fair to expect all leadership candidates to be transparent, come under scrutiny, because we will do as leader of the party and indeed as prime minister, so we should be as open as possible to show where our donations come from,” she added.
“It’s important to do that because there’s always an assumption that you don’t get something for nothing in this world and those who donate to your campaign will expect to be repaid in some way in the future.”
Ms Long-Bailey was subjected to her own grilling by the veteran journalist, during which she declined to revise her 10/10 rating of Mr Corbyn, saying “it’s not Top Trumps”.
The shadow business secretary insisted she is not the “continuity Corbyn” candidate which some cast her as, dismissing claims she is the outgoing leader in a different wrapper.
“It’s not the same old chocolate Corbyn bar,” she said, before being grilled on the anti-Semitism that has blighted the Labour Party.
She admitted regretting not directly challenging a member at a recent event in Liverpool who claimed “members of the Israeli lobby” including Jewish Labour MP Dame Margaret Hodge had the greatest responsibility for preventing Mr Corbyn from becoming prime minister.
“In my response I thought at the time that I had been implicit in explaining why this particular gentleman was wrong but with retrospect I should’ve called that out directly because it was anti-Semitic,” she said.
“I should have challenged that specific element of that gentleman’s contribution directly and I wish I had done that because it was an anti-Semitic statement to make.”
Sir Keir continued to decline directly criticising Mr Corbyn, who led Labour to its worst general election defeat since 1935 but is still revered by some members who will choose the next leader.
But he did not deny that he was “appalled by the awfulness” of the outgoing leader, as has been claimed by Labour peer Lord Falconer.
And Sir Keir said it was “utter nonsense” that he had undermined Mr Corbyn by not towing the leader’s line when he said he would campaign to remain in any further EU referendum.
The final leadership contender, Lisa Nandy, subjected herself to Mr Neil’s scrutiny in January.
Members and supporters began receiving ballots on February 24.
Voting closes two days before the new leader is announced on April 4.