The Tories have reportedly accepted another £5 million from the donor who said Diane Abbott made him “want to hate all black women” and “should be shot”.
Frank Hester gave the party £10m last year, making him the Conservatives’ biggest donor.
According to Tortoise, the health company executive has donated a further £5m so far this year, although it is yet to be declared to the Electoral Commission.
The revelation has led to fresh calls for Rishi Sunak - who has said Hester’s comments were “racist and wrong” - to hand the money back.
Labour chair Anneliese Dodds said: “Frank Hester’s remarks were clearly racist, misogynistic and have no place in our politics.
“There is absolutely no excuse for the Conservatives accepting additional money from Frank Hester. They should pay this back before it hits the coffers.
“Rishi Sunak needs to pay back every penny, cut ties with Frank Hester and apologise unequivocally to Diane Abbott.”
Liberal Democrat chief whip Wendy Chamberlain questioned whether the Tories’ initial decision to defend Hester was linked to the extra cash.
She said: “The Conservative Party must urgently confirm whether these reports are true and if so hand this tainted money back.
“The Conservative Party has dragged its feet in condemning these racist remarks for what they are. If that was in any way linked to this £5 million donation it would show this scandal is even worse than we thought.
“People like Hester and his attitudes need to be nowhere near our politics. Conservative politicians need to learn that just because someone gives you millions of pounds that does not make the inexcusable, excusable.”
Post office minister Kevin Hollinrake said yesterday that he would be happy for the Tories to accept another £10m from Hester because “we don’t believe Mr Hester is a racist”.
A Conservative spokesperson said: “Declarable donations will be published by the electoral commission in the usual way.”