The Tories raked in over £5 million from significant donations in the final quarter of last year - nearly double the sum received by Labour.
David Cameron's party was handed £5.15 million compared to £2.67 million for the Opposition, according to Electoral Commission figures.
Some £2 million of Labour's gifts were from unions - including around £940,000 from Unite and £353,000 from Unison.
However, the party's income was topped up with £1.5 million of public funding, while the Conservatives received £303,000.
The Liberal Democrats declared £828,000 of gifts, and Ukip topped up £196,000 of donations with nearly £90,000 of public funding.
The SNP received £347,000, including £293,000 from the taxpayer.
The British National Party (BNP), which temporarily lost its status as a political party last month after omitting to pay a £25 registration fee, benefited from a £150,000 bequest.
The details cover donations of more than £7,500 accepted by parties between October and December 2015.
The Tories said Labour had received £4 million in donations above the threshold in the third quarter of 2015, of which £1.2 million came from unions.
Croydon South MP Chris Philp said: " It's no surprise that private and business donors are abandoning an increasingly extreme Labour Party.
"Their policies of more spending, more borrowing, higher taxes and printing money would threaten the financial security of every family and business in this country."