The British National Party says it does not know whether it has banked £200,000 after being bequeathed a flat by a supporter.
It was reported the party had sold the three-bedroom flat left by Alfred Starmore, a retired train driver.
Starmore, who died aged 77, has already left his life savings - some £200,000 - to the far-right party.
His local newspaper, the Chingford Guardian, said the proceeds from the flat sale would be added to the total, ending the party's debt problems.
It quoted the BNP's London spokesman, Steve Squire, saying: "Naturally we were delighted that he was so generous. We’re not in debt now. It’s fantastic.”
But BNP spokesman Simon Darby, the party's former Deputy Leader, would not confirm the record windfall.
"I don't know, to be honest," he said.
"We get that many now, I lost count."
An Electoral Commission spokesman said the donation would have to be reported later in the year.