The Conservative Party's income almost halved last year, dropping by almost £20 million to its lowest level since 2003, official figures showed.
Accounts for 2011 published by the Electoral Commission showed the party took in £23.7 million and spent £22.8 million - and had liabilities totalling £8.7 million.
A slump was expected as the 2010 figure of £43.1 million was swelled by donations to the general election war chest and the party lost state funding on taking power.
But the latest figure is £7 million lower than the year after the 2005 general election and the 45% reduction represents a wider dip in financial support.
Labour also saw income fall, from £36.3 million to £31.3 million, with its post-election slump tempered by defeat making it eligible for "Short Money" taxpayer support.
And despite losing state support, the Liberal Democrats drew in £6.2 million - well down on the previous year's £9.6 million but only just short of its 2009 total.
The biggest leap in fortunes was enjoyed by the Scottish National Party, which saw income more than double from £1.8 million to just over £5 million.
Its coffers were partly swelled by two separate £1 million donations.
Labour MP Simon Danczuk said: "It seems even the prospect of kitchen suppers with David Cameron in the Downing Street flat can't stop the slump in Tory donations.
"With donors now losing faith with David Cameron in the wake of the cash-for-access scandal and George Osborne's disastrous Budget, the news that donations have already halved since the General Election will be causing panic in Tory HQ.
"The Tories may try to win back their rich supporters by offering tax cuts for millionaires while millions pay more, but with a double-dip recession made in Downing Street it's clear that even their fat-cat donors are feeling let down by a Tory Party that promised change, but has failed to deliver."