 Following Kirby's re-election at the May 2015 general election, with a reduced majority of 690 votes, but increasing his share of the vote by 2.7%, he was appointed as an Assistant Government Whip on 13 May 2015.Kirby was opposed to Brexit prior to the 2016 European membership referendum.In July 2016, Kirby was appointed as Economic Secretary to the Treasury and City Minister.