Of Jewish origin, he was the leader of the opposition to Oswald Mosley's antisemitism and his British Union of Fascists' marches through East London.
During World War II, he gained further notice by leading 100 people to shelter from the Blitz in the basement of the Savoy Hotel, to persuade the Government to open the London Underground stations to anyone sheltering from the bombing, a practice which the Government had previously ruled out, but which then became widespread.
He was defeated when he stood for re-election in 1950 in the new constituency of Stepney; his old seat of Mile End had been abolished due to boundary changes.
Until 1957, Piratin was the circulation manager of the communist newspaper The Daily Worker, but he left early that year, ostensibly over a matter of process.
However, in 1991 he told Alison Macleod about his doubts at the time: "In 1956, Phil said, he drove to Oxford, to defend the Party line on Hungary at a meeting of undergraduates.