The Lib Dems have received their second biggest donation ever, from an academic who bequeathed the party £950,000.
George Watson, a former professor at Cambridge University and one time Lib Dem candidate, died in 2013, aged 86.
His gift was the single biggest sum reported in the Electoral Commission's table of party donations for the third quarter of 2014.
The Conservatives topped the table with £6.76m in donations, compared to Labour's £3.19m.
Professor George Watson, a former fellow in English at St John's College Cambridge, stood for the Liberal Party in the 1959 election.
His donation is the Lib Dems' largest since the party received £2.4m from Michael Brown, who was later convicted of fraud and is serving a seven-year prison sentence.
The new figures from the Electoral Commission also revealed the Conservatives received more than twice as much in donations as Labour between July and September 2014.
The Conservative Party received £6.76m while Labour received £3.19m.
The Lib Dems reported total donations of £2.75m, the SNP £1.57m and UKIP received just over £98,000.
Labour received the second biggest donation of the quarter, just over £500,000, from the shop workers union, Usdaw.
Figures in full
• Conservative Party - £6,757,289
• Labour Party - £3,188,931
• Liberal Democrats - £2,752,873
• Scottish National Party (SNP) - £1,572,825
• Co-operative Party - £415,114
• UK Independence Party (UKIP) - £98,387
• Green Party - £88,250
Source: Electoral Commission