He became a member of the Czechoslovak (People's) Socialist Party (ČSS or ČSNS) and later served as the Vice President of its Central Committee.

In late 1938, after the Munich Agreement and the dissolution of the ČSNS, he joined the recently formed right-wing Party of National Unity.

In 1945, Neuman became a member of the constituent national assembly and was re-appointed mayor of České Budějovice, serving from 1946 to 1948.

From 1948 to 1960, he was deputy chairman of the party, which had reverted to its former name, ČSS, and was a member of the National Front Action Committee.

From July 1960 to April 1968, Neuman served as Minister of Justice in the government of the Czechoslovak Socialist Republic (CSR) and simultaneously as the chairman of the ČSS.