In 1856 the partly elected unicameral Legislative Council was abolished and replaced with a new parliament with elected members of the Legislative Assembly and appointed members of the Legislative Council. Martin was elected as one of two members for Cook and Westmoreland. When that electorate was largely replaced by the single member electorate of Hartley, Martin successfully stood for the new four member electorate of East Sydney. He was subsequently the member for Orange, Tumut, Monaro, Lachlan and East Macquarie. In August 1856 he was made Attorney-General of New South Wales in the first ministry of Charles Cowper. The appointment was controversial, as Martin was the first holder of the office who had not been admitted as a barrister. He had to resign his seat as a result of accepting the office, however he was re-elected unopposed. The appointment was brief, as the government was defeated in a no-confidence motion in October 1856 and Martin returned to the backbench.