Ben Salah was a trade unionist (Tunisian General Labour Union, UGTT) who had been a member of the ruling Socialist Destourian Party (PSD) and minister of economic planning in the government of Habib Bourguiba.

In this role, he pursued a communitarian socialist policy, aiming for a more unified and enlightened society by the means of a strong government.

[1] Ben Salah was made responsible for the economic failure of the late 1960s, dropped from the government, expelled from the PSD and sentenced to 10 years of forced labour in 1970.

When the more reformist Mohammed Mzali became Prime Minister, he allowed oppositional parties to run candidates' lists in elections and announced to officially recognize them in case they won more than five percent.

A more moderate faction which disagreed with Ben Salah, broke away in 1981 and formed the Popular Unity Party (PUP), which gained official recognition in 1983.