The first prime minister of Senegal, Mamadou Dia, who has died aged 98, was at the centre of his country's first major post-independence crisis in December 1962, in which he unsuccessfully attempted to stage a constitutional coup against Senegal's first president, Léopold Sédar Senghor. It was taken at the time as a classic case of the difficulties of the division of power between president and prime minister, but there was also a serious liberal/radical policy divide. Although he never returned to a position of power, Dia remained an iconic figure in Senegalese politics whose place in the national pantheon was secure.
Mamadou Moustapha Dia was born at Khombole in the Thiès region in western Senegal, son of a Toucouleur war veteran turned policeman. He began his education in a Qur'anic school, before moving into western education at the William Ponty school, principal training ground of the elite in French Africa in the 1920s and 30s. As a low-caste "subject" (as opposed to the "citizens" of Senegal's four communes), his passing the baccalaureate was considered remarkable, and he trained as a teacher, becoming a head teacher before continuing to study economics in Paris.
Although he had dabbled in journalism during the Vichy regime, it was only after Vichy collapsed in 1943 that he became motivated to enter politics. He attached himself to the rising star of Senghor, who, as a Catholic in a largely Islamic country, valued having a widely connected and able Muslim as his deputy: Dia was also a fluent orator in the Senegalese language Wolof.
He joined with Senghor in founding a successful political party and became its first secretary-general, staying at Senghor's side through all the turbulence of nationalist politics in the 1950s. Dia represented Senegal in the French senate in Paris from 1948 to 1956, and after key territorial elections for self-rule he headed Senegal's government, where he continued until he became prime minister, in tandem with Senghor as president, when Senegal became independent in 1960. He was also vice-president of the abortive Mali Federation of Senegal and French Sudan (later Mali) until its collapse in September 1960.
The experience of the next three years proved the difficulty of power-sharing in young states, already demonstrated by the break-up of the Mali Federation. Dia retained control of the economy and began to implement some of the radical ideas he had articulated in his book Réflexions sur l'Économie de l'Afrique Noire, published in 1960, especially in the reform of the key groundnut sector. This not only offended vested interests of the marabouts, the powerful religious leaders who controlled the groundnut business, but began to worry the French. They were used to Senghor's armchair socialism, but Dia seemed to be taking socialism seriously, and autocratically.
A grave power struggle developed between the two former political allies, and, in December 1962, a group of dissident parliamentarians tabled a vote of censure on Dia. He responded by invoking executive powers and ordering the army to lock the assembly building before the vote could be taken. Senghor charged that this was an attempted coup, in turn calling out the army, which was in the majority loyal to him. Dia and several of his ministers were arrested and tried for treason, being sentenced to jail "in perpetuity". After a long period of incarceration in the eastern town of Kédougou, Dia was first brought back to Dakar, pardoned in 1974 and given amnesty in 1976.
His political power may have been broken but not his spirit. Although his attempts to form his own party in the 1980s, after Senghor's successor, Abdou Diouf, introduced multiparty democracy, failed miserably, Dia became a kind of doyen for Senegal's fractious opposition parties, gradually acquiring the role of national treasure, as he continued regularly to write diatribes in the local press well into his 90s. He was noted for his attacks on the neo-liberal economic policies of the current president, Abdoulaye Wade, who ironically had been one of the lawyers who defended Dia in 1963.
After his death there was a massive outpouring of sentiment in Senegal's newspapers, which may not just be due to his longevity, or admiration for his obdurate attachment to principles. Why, since these events were nearly 50 years ago, does Dia exercise such power over the Senegalese political imagination? There is a measure of guilt, even a feeling that, although he was mistaken and stubborn in pushing his political showdown with Senghor, the constitutional crisis was not quite a coup, and the punishment was certainly too harsh.
• Mamadou Dia, politician, born 18 July 1910; died 25 January 2009