Tory MP Alan Duncan is suing Telegraph Media Group for libel over a story published in the Daily Telegraph.
Duncan, the shadow secretary of state for business, enterprise and regulatory reform, is demanding unspecified damages.
He claims that a front page story headed: "Cameron tries to steady Tories as EU sleaze scandal spreads", and an inside page story: "Second shadow cabinet member in sleaze inquiry", were defamatory.
Duncan, the MP for Rutland and Melton, is also suing over two online stories headed: "Conservative front bench MP in sleaze inquiry" and "How can we rid politics of sleaze?"
He is seeking an injunction banning repetition of the allegations at the centre of his claim.