From 1921 to 1937, he was a member of the Executive Council of the PPS. In 1930 he was arrested along with a dozen other socialist leaders and held at the Brest Fortress, as part of the Sanation government's manoeuvre to clamp down on the opposition under accusations of an attempted coup. At the Brest trials, he was convicted and sentenced to three years in prison. However, he was given the option of going into exile. From 1933 to 1935, he was exiled in Paris and later returned to Poland and gave himself up for incarceration, which was commuted to several months during 1935.