Ken Livingstone has likened Dan Jarvis receiving donations from a hedge fund guru to "Jimmy Savile fundraising [for] a children's group".
The former London Mayor attacked ex-Paratrooper Jarvis for taking £16,800 from one of Labour's biggest private donors, whom he branded one of "the most rapacious and damaging form of capitalists."
Speaking on Thursday night he told LBC's Iain Dale: "The other thing you have to say about Dan Jarvis: If you're really Labour what are you doing taking donations from hedge fund managers - the most rapacious and damaging form of capitalists that we've had.
"It is absolutely bizarre. It's a bit like Jimmy Savile fundraising [for] a children's group."
It came a week after news Martin Taylor, a man who donated £600,000 to Labour under Ed Miliband, gifted a significant sum to the Barnsley MP, a move viewed by some as grooming him to challenge Jeremy Corbyn for the leadership.
The MP was criticised for taking money from Taylor
Jarvis was defended by fellow MP Ian Austin after left-leaning comedian Matt Forde joked the news was representative of Labour's new "kinder politics".
Jarvis made a speech on Thursday widely seen as his first step in a bid to take over from Corbyn, in which the MP warned that Labour faced a “major test” in May’s elections.
In a significant move to raise the bar for the elections on May 5, the former shadow minister said his party should be “taking” not losing councils in England and should be making “progress” in Scotland.