He founded the HaMa'avak pioneer group, and in 1948 was amongst the founders of Alonei Abba.

From 1951 until 1961 Sha'ari was a member of the Histadrut's Organising Committee, and between 1957 and 1961 headed its Pensions and Legal departments.

Shortly before the 1965 elections Sha'ari and several other Progressive Party members left the Liberal Party to establish the Independent Liberals, with Sha'ari becoming head of its Economic Committee.

He was re-elected on the new party's list in the elections, and on 17 January 1966 was appointed Deputy Minister of Development.

Sha'ari also served as chairman of the board of directors at the Israel Electric Corporation and the Development and Tourism Company.