In the years before World War II, he was an anti-war activist, joining the Cambridge Scientists Anti-War Group. He joined the Communist Party, until the invasion of Poland by the Soviet Army in September 1939. Formerly classified UK security service papers reveal that Wilkins came under suspicion of leaking atomic secrets. The files, released in August 2010, indicate surveillance of Wilkins ended by 1953. "After the war I wondered what I would do, as I was very disgusted with the dropping of two bombs on civilian centres in Japan," he told Britain's "Encounter" radio program in 1999.