Poland last night unseated Jaroslaw Kaczynski, the nationalist Prime Minister who has made enemies across the European Union, in an extraordinary election that brought a landslide victory for his main conservative rival, Donald Tusk.

Early exit polls showed that Mr Tusk’s Civic Platform party would probably be able to rule Poland without a coalition partner – reducing some of the political acrimony and friction that has soured the country over the past year. “The result should mean a period of stable political rule,” said a relieved EU diplomat. Mr Kaczynski – the twin brother of President Lech Kaczynski – has irritated Russia, Germany and Brussels with his fierce defence of Polish national interests.

He was removed from power by young voters, hundreds of thousands of whom have been flying in from Britain and Ireland over the past few days in order to cast their ballots in their home towns. Thousands more queued to vote in Polish consulates. This ensured a victory for Civic Platform in Warsaw – overseas votes count towards the result in the Polish capital – which set the tone for a day in which Mr Kaczynski’s Law and Justice party lost most of its strongholds.

Exit polls awarded 43.7 per cent to Civic Platform, compared with 30.4 per cent for the Law and Justice party. In theory Mr Tusk could form an alliance with the third-place Left and Democracy party, which won 13.3 per cent of the vote, or the Peasants’ Party (PSL), which picked up just over 8 per cent. Neither of Mr Kaczynski’s former coalition allies – the clericalist League of Polish Families and the rural Self-Defence grouping – won enough votes to be represented in parliament. Mr Kaczynski is therefore left without any significant partner.

The election ushers in the beginning of the end politically for the Kaczynski twins, who for the past year have ranked as the most bizarre governing tandem in Europe. The President will stay in power until 2010 and will form an uneasy cohabitation with the Tusk Government. In theory he will be able to block, at least for a short while, some foreign policy initiatives. Insiders say that Mr Tusk is likely to choose Radek Sikorski – who made his name as a journalist in Britain in the 1980s – as Foreign Minister.

The election split Polish families because it was focused on personalities. Until last week it appeared that Mr Kaczynski had the edge. His voters, often devout Catholics, were the most disciplined in Polish politics. If turnout was to be as low as two years ago – 40 per cent – and the urban young stayed at home, there was little to stop Mr Kaczynski. But turnout was strong, at 55.3 per cent.

The turning point may have come last week when the government-backed Central Anti-Corruption Bureau revealed details of a “sting” operation in which an undercover agent courted a female Civic Platform candidate, persuaded her to accept a bribe and then arrested her for it. For many urban voters that was a step too far.

“I was going to vote for the Kaczynskis because they really are doing something about corruption that should have been done years ago,” Stanislaw Pruszynski, who runs a restaurant business in Warsaw, said. “But I have switched to the Civic Platform even though they don’t have a proper programme – the Kaczynskis have gone too far by smearing their opponents.” One powerful factor was also the politicisation of the Poles working abroad. “This was too important; we couldn’t let the twins tarnish the Polish image any longer,” said Mariusz Radomski, arriving in Warsaw on Saturday from London.

The Civic Platform has been active in trying to persuade young émigrés to return home. Poland is preparing to adopt the euro and its new ruling party wants to bring troops back from Iraq and intends to renegotiate an agreement with the US to house missiles on Polish soil.

Thousands of Poles queued for hours in Central London to vote after officials underestimated numbers. Only 11 polling booths were opened at the Polish Consulate and Embassy although there were more than 12,000 registered voters in the area. Voters arrived by bus from Brighton and other cities and police were called in to control traffic. Polls were due to shut at 8pm but remained open until the last person had voted. “It’s one of the important things to do if you want to call yourself a citizen of Poland,” Daniel Tokarczyk, 27, of Krakow, said.

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