The Conservatives received 23.7 million pounds ($36.7 million), down from 43.1 million pounds in 2010, when party coffers were boosted by donations for the general election campaign.
The opposition Labour Party saw donations decline to 31.3 million pounds, while the Liberal Democrats, the junior partner in the coalition government, attracted 6.2 million pounds, a third less than in the previous year.
While Cameron does not face national elections until 2015, support for the Conservatives has fallen sharply following an unpopular budget in March and poor news on the economy.
A YouGov Plc poll completed on July 23 gave Labour 43 percent support, the Conservatives 33 percent and the Liberal Democrats 9 percent.
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