More than half the donations raked in by David Cameron's Tories last year came from the City, research has suggested.
Financial services firms and individuals donated £11.4m to the party in the first nine months of 2010, according to figures compiled by the Bureau of Investigative Journalism.
That was 51% of the total £22.5 million raised over the period - up from a quarter in 2005.
Stuart Wilks-Heeg of Liverpool University said: "Given we have just experienced a blow-out in the financial system and are witnessing an ongoing struggle over its regulation, the scale of Tory party funding from the City must be an issue."
But a Conservative Party spokesman pointed out that George Osborne had just upgraded the bank levy.
"On the day that the Chancellor raised another £800 million in tax from bankers, and after he has introduced the toughest rules on bankers' pay anywhere in the developed world, it beggars belief that anyone could claim that Conservative donors are influencing policy," the spokesman said.
The Tories' close links with the City are well known. Two of the Square Mile's biggest names, Icap boss Michael Spencer and hedge fund guru Lord Stanley Fink, have held the post of party treasurer in recent years.
The coalition is currently embroiled in tough negotiations with banks over their bonus payouts, tax contributions, and business lending.
However, the research indicated that the majority of big-ticket donors are hedge fund managers and brokers rather than bankers.