A member of the Labour Party he was elected to Stepney Borough Council (1934-37) and Lambeth Borough Council (1937-56). During the Second World War Lipton served in the British Army and reached the rank of Lieutenant Colonel.
On 23rd October, 1955, the newspaper, New York Sunday News, reported that Kim Philby was a Soviet spy. Two days later Lipton asked Anthony Eden in the House of Commons: "Has the prime minister made up his mind to cover up at all costs the dubious third-man activities of Mr. Harold Philby". Eden refused to reply but, Harold Macmillan, the foreign secretary, issued a statement a couple of days later: "While in government service he (Philby) carried out his duties ably and conscientiously, and I have no reason to conclude that Mr Philby has at any time betrayed the interests of his country, or to identify him with the so-called 'Third Man', if indeed there was one."
Kim Philby now called a press conference where he denied he was a spy. He added that "I have never been a communist and the last time I spoke to a communist knowing he was one, was in 1934". Philby accused Lipton of lying and challenged him to repeat his claims outside the protection of the House of Commons. Lipton was forced to issue a statement where he withdrew his comments about Philby.
Marcus Lipton remained in Parliament until his death on 22nd February, 1978.