French Foreign Minister Laurent Fabius has announced the death on Friday of Pierre Mauroy, France's first ever Socialist Prime Minister.
Mauroy, who was 84, had been admitted to hospital in Paris last weekend, suffering fatigue from the effects of cancer treatment. He had undergone surgery on a cancerous tumour on his lungs in April 2012.
Mauroy was Prime Minister under President François Mitterand between 1981 and 1984, and mayor of the northern city of Lille from 1973 to 2001
President Francois Hollande, who is on an official visit to Japan, said Mauroy was "a man who had served France during exceptional times."
Mauroy "took courageous measures... he served his country without ever undermining its fundamental values," Hollande said.
For his part, Fabius, who succeeded Mauroy as French prime minister, described him as "a pillar of democratic socialism who has left us," and someone who "had the Left firmly rooted in his heart."
Mauroy's government cut the legal work week from 40 hours to 39, lowered the retirement age to 60, and extended the period of paid holidays by a week to five weeks.
It also greatly extended family benefits, increased the minimum old-age pension by 30 percent and broadened health care coverage with health insurance benefits made more widely available to part-time workers and the unemployed.
He is also credited in the 1980s with persuading British prime minister Margaret Thatcher to sanction the building of the Channel tunnel.
But his efforts to improve the French economy by boosting domestic consumption did not work in the long run and Mauroy was forced to undertake a series of austerity measures.
Mauroy began his career as a teacher and soon led the Young Socialist Movement. He rapidly rose within the party and became the second most powerful person in the Socialist Party in 1971 after Mitterrand.
Although the two men had an "exceptional friendship", Mauroy said, there were points of conflict as well.
"I have had many differences with Francois Mitterrand, much more than is generally known," he said.