In 1955 he became a member of the Political Bureau of the Algerian Communist Party and in December his support for the independence struggle was forced underground.

The Organisation of Popular Resistance had been created by Mohamed Harbi and Hocine Zahouane, two left-wing leaders of the FLN to oppose Boumedienne's coup.

President Boumediène also made Algeria closer to the Eastern bloc of the USSR and all these steps pleased indirectly Sadek Hadjeres' PAGS party which found a favourable political terrain to advance its ideas, while still remaining an opposition closely watched by the government and excluded from all official activities and subject to repression like all other opposition parties.

In 1976 during the debate on the national Charter, Hadjeres led the underground PAGS briefly out of clandestinity by expressing loudly its views via student organisations such as the UNJA.

The fact the FLN supported the freedom fighters in Afghanistan combating the USSR only served to sour relations further with Sadek Hadjeres and his PAGS party.

His re-entry on the Algerian political scene occurred however at a time when the Berlin Wall was falling and his communist convictions were several shaken by the birth of a new era.

His communist PAGS party was in this context severely defeated at the 1990 and 1991 elections by the Islamic Salvation Front (FIS) and Hadjeres decided to pull out of politics in 1991.

When the government and the army cancelled the elections in 1992, they asked for Hadjeres' vocal support but he refused to give it, even though he was condemned to death by several Islamist para-military and then terrorist organisations (MIA, FIDA, GIA etc...).

The PAGS party ceased all activity in 1992 and Hadjeres himself left Algeria and settled in France where he undertook work as an associate lecturer and researcher in geopolitics with the CRAG centre of Paris 8 University (Centre de recherches et d’analyses géopolitiques à l'Université de Paris VIII).

Sadek Hadjeres continued to be a very influential figure for Algerian communists and members of the MDS until his death, although he did not take part officially in any more political activities.