When former Northern Ireland Secretary Roy Mason announced his retirement in October 1986, Illsley was nominated by the NUM in the selection of a Labour candidate for Barnsley Central. He was viewed as being on the left of the Labour Party while his main opponent was Ronnie Fisher, a Barnsley Borough councillor identified as a moderate. The general secretary of the Yorkshire NUM, Sam Thompson, wrote to NUM members encouraging them to attend the selection meeting in January 1987,"Miners' MP lobby", The Times, 2 January 1987. Illsley was selected and then easily elected to the House of Commons in the general election in June 1987. He was on the frontbench while Labour were in opposition, but was a backbencher after they won power in 1997. He voted against the privatisation of the National Air Traffic Services (NATS).
