The leader of Poland's liberal Civic Platform party, Donald Tusk, has been nominated as the country's next prime minister by President Lech Kaczynski.
Mr Tusk has pledged to mend strained ties with the EU
The Civic Platform won last month's parliamentary elections, but did not secure enough seats to govern alone.
Mr Tusk is expected to form a coalition with the smaller Peasants' Party.
Prime Minister Jaroslaw Kaczynski, the president's twin brother, tendered his government's resignation on Monday after serving two years in office.
The election was called two years early after Mr Kaczynski's coalition collapsed over a corruption probe.
In a brief ceremony in the capital, Warsaw, Mr Tusk was nominated as the country's 14th prime minister since the collapse of communism in 1989.
Under the constitution, the 50-year-old historian has a fortnight to form a government which is able to secure parliamentary approval.
Mr Tusk has promised to improve strained relations with Poland's European neighbours and take advantage of the country's strong economic growth.
President Kaczynski (L) may clash with the new government
In his election campaign he attacked his predecessor's "incompetent" foreign policy, which he said had tarnished Poland's image abroad and harmed relations with neighbouring Germany.
The Civic Platform plans to lower taxes and reduce bureaucracy in a drive to speed up the pace of Polish economic reform.
Mr Tusk has also pledged to withdraw Poland's 900-strong military commitment to Iraq in 2008.
However, his new government may face difficulties in implementing bold reforms, analysts say.
President Kaczynski will have the power to veto bills and he has said he will do so if Mr Tusk tries to introduce "liberal" policies such as a flat-rate income tax.
In his resignation speech, Mr Kaczynski's brother, Jaroslaw, said his government had made key achievements under "difficult circumstances".
"We have ended our mission in government with our heads held high. The economy is in fine form and the past two years have reinforced Poland's position in Europe," he said.