The Conservatives received more than half the total donations
Political parties received £10.7m in donations between April and June - up from £8.1m during the previous three months, figures show.
The Conservative Party was given £5.6m, while Labour received £3.8m and the Liberal Democrats £945,192, according to the Electoral Commission.
Labour's debt stands at £17.9m, the Conservatives' at £12.1m and the Lib Dems' at £1.1m.
Some 31 registered parties failed to provide donation details on time.
This was down from 37 in the previous quarter.
The commission's chief executive, Peter Wardle, said: "Having previously called on parties to address the issue of late reporting of individual donations, we are pleased to see this being addressed and expect to see continued improvements."
For Labour, high-profile donors include comedian Eddie Izzard, who gave just under £10,000, and Steve Lazarides, the grafitti artist Banksy's dealer, who gave just over £120,000.
Businessmen Nigel Doughty and Sir Ronald Cohen, both of whom are regular donors, provided £250,000 each - but the bulk of the party's money has come from the unions.
High-profile donors to the Conservatives include Dave Whelan, the chairman of Wigan Athletic FC, who gave £250,000.
The BBC understands that loans made to Labour by Lord Sainsbury and Sir Gulam Noon - worth £2m and £250,000 respectively - have been converted into donations.
These were made around the time of the last general election, in 2005, before loans worth more than £5,000 had to be made public, under the terms of the 2006 Electoral Administration Act.
Meanwhile, the Liberal Democrats have defended taking money from foreign businessmen - despite it being party policy to crack down on tax exiles.
According to the commission, Bhanu and Sudhir Choudhrie - non-domiciled taxpayers - gave £20,000 each to the party.
A Lib Dem spokeswoman said the two men were on the electoral register in London, and so the party had stuck to the current rules.
The Scottish National Party declared donations worth £13,627 from April to June, while Plaid Cymru declared nothing.
The figures do not include public funding, known as Short money, which totalled £1.3m for the Conservatives, £132,156 for Labour and £637,625 for the Lib Dems.
The SNP was given £81,073 and Plaid Cymru £60,027.
During the first quarter of the year, the Conservatives received £4.2m, with Labour on £3m and the Lib Dems on £470,000.