Malthouse was elected to Westminster council in May 1998, representing St George's ward in the Pimlico area of central London. Following boundary changes, he was re-elected in May 2002 for Warwick ward, which is also in Pimlico. Malthouse was appointed as Chief Whip of the Conservative Group, and following a change of leader to Sir Simon Milton, he was appointed Chairman of the Social Services Committee. Two years later, he was elected Deputy Leader of the Council and became Cabinet Member for Finance.