While the rest of the family moved back to Moscow in 1928, he attended high school in Lahr where he joined the Young Communist League of Germany (under a false name, since he could not do so legally as a Soviet citizen) and received German Abitur in 1931.

Simultaneously, and together with his brother Stefan, in 1943 he also joined the newly organized Polish Workers' Party, a choice he later explained as driven by his deep belief in the righteousness of Communism despite his first-hand experience of the Soviet regime's atrocities under Stalin.

In 1958 he became head of the international department of Nowe Drogi [pl], a monthly publication of the Central Committee of the Polish United Workers' Party.

In the ensuing years, he became increasingly active as a translator and conference interpreter in matters of socio-political, historical and economic analysis, and remained involved in those areas well into his retirement.

Late in his life, together with his brother Stefan Leder [pl] who in the meantime had become a noted psychiatrist, he coauthored a book on their family members' history and lifelong commitment to Communism, first published in German as Unbeirrbar Rot: Zeugen und Zeugnisse einer Familie (2002, ISBN 3929390620) and then in Polish as Czerwona nić: Ze wspomnień i prac rodziny Lederów (2005, ISBN 8320717892).

In 1980-81 he was involved in what became known as the "horizontal movement", an attempt at reforming the Polish United Workers' Party from within, whose name hinted at alternative structures to democratic centralism.

[1] He died in 2007 and was buried at the Powązki Military Cemetery in Warsaw (section A2-8-6), together with his aunt Edda Tennenbaum [de] (1880-1952), also a communist activist, and later joined by his wife Ewa Lipińska (1919-2012), a microbiologist.