The Tories outspent Labour and the Liberal Democrats' combined total expenditure at the general election.
The Conservatives spent over half of total spending by parties at a national level last May. Labour contributed just over a third of the total amount, while the Lib Dems spent only 15%.
Yet total campaign expenditure by parties actually fell to £31.5 million, around £10.8 million less than in 2005.
The Electoral Commission found almost all of this drop was due to a £9.9 million decrease in Labour's spending.
Across the UK, 138 political parties fielded candidates. Only 11 of the parties succeeded in having their candidate elected to parliament.
The main three political parties accounted for 94% of all party expenditure and 98% of all seats won.
Over £59 million was spent at the UK general election in total, including candidate expenditure and donations by third parties.
Non-party campaigners contributions grew to over £2.8 million, more than £1 million more than in 2005.
Four thousand one hundred and fifty candidates stood at the UK general election, spending just over £25.2 million. Most of this expenditure was on 'unsolicited material' like leaflets.
The Electoral Commission regulates campaign spending in UK elections. Candidates are required to file expenses and political parties face a spending limit depending on the number of seats they are contesting.
Any third-party planning on contributing over £10,000 in England - or more than £5,000 in Scotland, Wales or Northern Ireland - must register with the commission. Thirty-three campaigners were registered before last year's election.
Peter Wardle, chief executive of the Electoral Commission, said that transparency on campaign expenditure was crucial to the UK's democracy.
"Transparency about the reporting and analysis of who spends what at elections is important for a healthy democratic system that commands public confidence," he said.
"In 2011 we will continue to focus on ensuring the fundamentals of the UK's regulatory regime for party and election finance - transparency, controls on donations and spending, and enforcement - are as robust as they can be."