The Justice Secretary insisted it was "never true" to suggest people who contribute cash to Conservative coffers would receive policies in return, adding donors give money as they believe a Tory government is "best for Britain".
Labour has sought to step up pressure on the Prime Minister by accusing him of seeking to finance the Tory campaign with Russian funds, while £160,000 was paid to the party by a Russian oligarch's wife in return for a tennis match with him and the London Mayor. Mr Cameron has insisted Vladimir Chernukhin, who served as deputy finance minister in Vladimir Putin's first administration, is not a crony of the Russian president and it would be "the wrong thing" to give the money back.
Asked if the tennis match is going ahead, Mr Grayling told BBC Radio 4's Today programme: "Well, the tennis match is going ahead because it's a donation from a British woman, a British citizen who is perfectly entitled to make a donation. In that particular case this was a British woman who happens to be married to a former Russian minister."