When the Labor Party eventually regained office under McKell, defeating Alexander Mair and the UAP at the May 1941 election, Heffron was elevated to the ministry as Minister for National Emergency Services, charged with the implementation of the National Emergency Services Act, and the administration of National Emergency Services, New South Wales. In this role he was responsible for the civil defence and air-raid precautions of New South Wales, which became increasingly more important after the entry of Japan in the Second World War in December 1941 and subsequent attacks on Australia on Darwin and Sydney in 1942. Serving until 8 June 1944, Heffron advocated public vigilance whilst in this portfolio, declaring: "We are living in a fool's paradise in Australia ... Many people have the idea that what is happening in other countries cannot happen here."