Rishi Sunak is under fresh pressure over his ties to Frank Hester – the party donor embroiled in a race row – amid reports his party received £5m more than previously known.
The Conservative Party has not denied a Tortoise Media report that it has received more from Mr Hester than the £10m he gave last year.
Gifts to parties made up until March do not have to be published until June.
Labour and the Lib Dems say the Tories should hand all his money back.
Mr Hester donated £5m to the party last May, with a further £5m donated through his company in November.
According to parliamentary records, he also gifted the prime minster the use of a helicopter for a political visit in November, valued at £15,900.
Tortoise Media has now reported that the party has received a further £5m cash donation from him, which has not yet been disclosed, taking his total contribution to £15m over the last year.
However, it is unclear whether the money has yet been paid. One source told the BBC it has been, but another said although the Tories expect to receive more cash, no money has yet been sent.
Donations made up until March are not due to be published by the elections watchdog until June, due to the three-month lag before they are made public.
Mr Hester allegedly said veteran MP Diane Abbott made him “want to hate all black women” and should “be shot”, sparking days of fierce backlash.
The tech boss apologised for making “rude” comments about the former-Labour MP but said his remarks “had nothing to do with her gender nor colour of skin”.
The prime minster called the comments “racist” and “wrong” but argues Mr Hester’s apology should be accepted.
Speaking to reporters on Friday, Chancellor Jeremy Hunt refused to say whether the Tories had accepted a further £5m from Mr Hester.
He said the party was committed to following the rules on reporting donations, and any gifts received would be declared “when the time is right”.
‘No excuse’
Mr Sunak rejected repeated requests to hand back Mr Hester’s donations during a fiery Prime Minister’s Questions session on Wednesday.
Responding to the BBC’s query on Thursday about a possible further donation from Mr Hester, the Conservatives provided a one-line statement: “Declarable donations will be published by the Electoral Commission in the usual way.”
One of the Conservative Party’s biggest donors, the £10m he is known to have given the party last year represents around a fifth of all donations to the party that year, which totalled £48m.
He is the founder and chief executive of TPP, a Leeds-based health tech company that is a supplier of records management systems to the NHS.
On Friday, the British Medical Association body representing UK GPs passed a motion calling on him to resign, and urging GP practices to “consider” his alleged comments before signing new contracts with his company.
Labour Party chair Anneliese Dodds said: “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.”
The Liberal Democrats said if the donation is confirmed “it would show this scandal is even worse than we thought”.
Lib Dem MP Wendy Chamberlain said: “People like Mr 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.”
