The sources of donations to the main political parties were revealed on Friday.

A report from the Electoral Commission revealed that large donations from trade unions have put Labour well ahead of the Tories in the cash stakes.

But, the Tories are still in receipt of the biggest cash payments from wealthy individuals and business, the figures show.

Whilst cash from the unions led to Labour receiving four times as much in donations as the Conservatives, the support of individuals such as the millionaire Stuart Wheeler has filled the Tory coffers ahead of the general election splurge.

Since February, Labour has received £2.4 million in donations, compared to £638,000 for the Tories and less than £200,000 for the Liberal Democrats. More than half of the Tories' donations came from individuals rather than companies.

The biggest single sum recorded during the period was a £555,000 donation from the GMB to Labour.

The disclosure follows new rules which requires all political parties to reveal who made donations of £5,000 and above.

The Lib Dems' campaigning chief Lord Rennard said that transparency was welcome but said he was still hesitant about the motives of millionaires who bankroll political parties.

He said: "There has been widespread public concern about what millionaire donors may want in return for their money. They may hope to influence a party's policy or the choice of party leaders. This can bring politics and politicians into disrepute."

Labour and the Tories have faced funding rows over recent months. Tony Blair faced accusations of sleaze after it emerged that three wealthy Labour supporters were to donate £2 million each to the party. William Hague came under fire after it was revealed that the spread-betting tycoon Stuart Wheeler was to bankroll the Conservatives ahead of the general election.

The Tories seized on the publication of the figures, claiming that they showed Labour was still in hock to its trade union paymasters.