He was Minister of Home Affairs 1939–43 and January–June 1948, as well as Minister of Justice 1945-June 1948.
Lawrence had his spleen damaged when he was attacked by Nationalists at a political meeting during the Second World War. This injury caused Lawrence continuous pain, as he explained when he declined to be considered for the Progressive Party leadership in 1959. He did, however, become the first party chairman of the PP.
Lawrence, like all the Progressive MPs except Helen Suzman was not re-elected at the 1961 General Election. He did not return to Parliament but served as temporary Party leader after Jan Steytler resigned in December 1970, until Colin Eglin was elected leader in February 1971.