Cold on missile defence
He said the centre-right party could also break the outgoing government's negotiations with the US on hosting a missile defence system on Polish soil unless Washington offered sufficient security trade-offs.
The party has promised to speed up economic reforms and analysts expect tax cuts and privatisation that would also help the country of 38 million towards adopting the euro currency.
|Jaroslaw Kaczynski conceded defeat but |
vowed to be a "tough" opposition [AFP]
And it aims to rebuild ties with EU partners such as Germany that have been badly strained under Kaczynski and his twin brother Lech, the president.
The election which was called two years early after the last coalition collapsed amid acrimony over a corruption investigation, deeply divided the nation.
Kaczynski's party was strong in rural areas feeling left out by post-communism changes and among older and more religious Poles while the opposition appealed to the younger and urban voter.
In the end though, the biggest turnout for parliamentary polls – 55 per cent – since the fall of communism nearly two decades ago, appeared to be a strong voice for change and a rejection of two years of turbulent rule by the nationalist Kaczynskis.
Jaroslaw Kaczynski conceded defeat. "We have failed against a wide front," he said, but added: "We will be a decisive, tough opposition."
His brother Lech does not face a presidential election until 2010 but opposition parties together looked set to get enough seats to trump his power to veto legislation.
Tusk, expected to be the next prime minister, said: "For many weeks we have been convincing Poles that life in Poland can be better, that Poles deserve a better government.
"We are moved that Poles went to cast their ballots."
The Civic Platform appeared to be a few seats short of being able to govern alone, but should form a coalition easily with either the centrist Peasants' party or a leftist bloc.
It was the best result by any party in the post-communist era. Full results are expected on Tuesday.