New figures released by the election watchdog show the Conservatives accepted £123,464 from Lord Ashcroft, the deputy chairman of the party, who is spearheading the battle for the key marginal seats.
The Electoral Commission figures show that on 31 March this year, David Cameron boosted his election war chest with a donation from Bearwood Corporate Services, the company through which Lord Ashcroft has donated millions of pounds to the Tories in the past.
Douglas Alexander, Labour general election co-ordinator, said: "David Cameron just doesn't get it. The moment the spotlight stopped being on Lord Ashcroft, the Conservatives started taking his money again."
The Commission's accounts revealed the Tories had raised more than £16.6m – three times the amount that the Labour Party have raised. The Tory fundraising effort has dwarfed Labour's donations with a total £12.3m raised in the first quarter of the year, and a further £4.3m since the election was called.
Labour raised £4m during the first quarter of the year with over 70 per cent coming from the unions and a further £3.6m after the election gun was fired. Nick Clegg's Liberal Democrats raised £1.9m during the first quarter of the year and £204,000 after the election campaign was launched.
Labour did better in the third week of the campaign, raising £1.4m compared to £645,250 by the Conservatives. Unite – Britain's biggest union – gave £1.5m in the first quarter of the year, 40 per cent of the total raised in the period. Charlie Whelan, Gordon Brown's former spin doctor, is the union's political director, and Unite has been accused of gaining influence within the Labour Party for a possible leadership election after Thursday's poll by sponsoring up to 59 candidates.
The Liberal Democrats' main donors included two UK-based companies, C & C Business Solutions and C & C Alpha Group, venture capital businesses, run by a prominent Indian "non-dom" family who donated more than £220,000 during the first quarter of the year.
It led to Tory accusations of "hypocrisy" against Nick Clegg, the Liberal Democrat leader. Mr Clegg has criticised the Tories for accepting money for the battle in the marginal seats from Lord Ashcroft, who is non-domiciled in the UK for tax purposes. However, the Electoral Commission confirmed that it was acceptable to channel funds through UK-based companies.
The Green Party received £59,650 during the first quarter of the year.