 Cairns was the Conservative Party's candidate for the Vale of Glamorgan at the 2005 general election, and was re-selected as Parliamentary candidate for the seat in July 2007.Cairns was suspended as the parliamentary candidate while the party carried out an investigation over his radio comments; he was reinstated as the parliamentary candidate on 22 October 2008.Cairns was elected as the MP for the Vale of Glamorgan at the May 2010 general election, gaining the seat from Labour with a majority of 4,307.