Bronislaw Geremek, a leading thinker in Poland's anti-communist Solidarity movement and a former foreign minister, was killed in a car crash on Sunday aged 76.
Geremek had been driving his Mercedes saloon near the western Polish town of Lubien when it veered into the opposite lane and collided head-on with an oncoming van, police spokeswoman Hanna Wachowiak told Reuters.
Polish President Lech Kaczynski, a political opponent of Geremek's, said he was "deeply saddened" by the news.
The European Commission and France, which holds the EU's rotating presidency, hailed Geremek as "a great conscience" of his country for his championing of liberal democracy under the communist regime and his later advocacy of European unity.
"He was a European of exceptional stature, a Pole of unwavering convictions. All his life he demonstrated political courage without compromise," said Jose Manuel Barroso, president of the European Commission.
"I hope future generations remember Bronislaw Geremek as an example of a free spirit and that he stays in our memory as one of the most powerful symbols of liberation against all oppression."
The bearded, pipe-smoking Geremek was a respected historian and author of numerous books, including on mediaeval European history, his academic speciality. He also sat in the Liberal group in the European Parliament.
"He was a friend of old, a great conscience of Poland, one of the great intellectuals of central Europe," French Foreign Minister Bernard Kouchner and France's European Affairs Minister Jean-Pierre Jouyet said in a joint statement.
Geremek had belonged to the reform wing of Poland's ruling Communist Party as a young man but quit in 1968 to protest against the Soviet invasion of Czechoslovakia and the extinguishing of that country's democracy movement.
He later became a key adviser to Lech Walesa and the Solidarity trade union, taking part in the round-table talks that led to the first partially free elections in postwar Poland and the end of one-party communist rule.
Geremek served as foreign minister from 1997 to 2000, overseeing Poland's accession to NATO.
"Geremek was a sensitive, deeply cultured person who combined many talents," said Wladyslaw Bartoszewski, another former foreign minister and a survivor of the Nazi Holocaust.
"He was the kind of person I was happy to have on my side, rather than as an opponent."
Geremek clashed with Poland's previous conservative of government of Jaroslaw Kaczynski, twin brother of President Kacyznski, over his refusal to declare he had never collaborated with the communist secret service under a new vetting law.
Geremek received strong support from fellow MEPs and Poland's Constitutional Court later struck down much of the law.Reuse content