Donations to the Conservative Party were more than double Labour's during the opening three months of 2017, official figures show.
The Electoral Commission said Theresa May's party received £5.46 million from donors between January and March, with mining millionaire Michael Davis providing the biggest gift at £317,000.
Unions helped Labour to raise £2.64 million, with Unite donating £657,702 and Unison £376,242.
Former motor racing boss Max Mosley, who has used family money to fund press regulator Impress, also gave Labour £300,000.
The commission said total donations accepted by political parties in the three-month period was £9.39 million.
The Liberal Democrats received £603,155, the Co-operative Party - which has links with Labour - £322,800, Ukip £246,910, the Green Party £58,170, Plaid Cymru £23,000 and the SNP £3,300.
Public funds are also listed for each party, which predominantly boost the totals for opposition parties.
The Women's Equality Party received donations amounting to £10,000 while the Socialist Party of Great Britain reported £19,816, the Electoral Commission said.
The regulator released figures earlier this week showing donations for the opening days of the General Election campaign - from May 3, when Parliament was dissolved, until May 9.
This revealed the Tories had received £4.1 million in donations compared to Labour's £2.7 million.