Poland's governing right-wing Law and Justice party (PiS) won European elections, complete official results have shown, with its leader Jaroslaw Kaczynski urging a wider victory in the autumn general ballot.

The PiS took 45.38% of the vote to win 27 of Poland's 51 seats in the European Parliament compared with 38.47% and 22 seats for the liberal European Coalition, according to full official results published today.

The progressive Spring party, led by openly gay former MP and mayor Robert Biedron, took 6.06% for three seats while the far-right Confederation group failed to cross the five-percent threshold required to enter the European Parliament.

Poland will gain one extra seat for a total 52 MEPs after Brexit.

"We won but with a result that should push us to one thing: to work hard before the parliamentary elections this fall," Mr Kaczynski said at PiS campaign headquarters in Warsaw as an exit poll handed his party victory.

This is the first time the PiS has topped the European polls amid a record voter turnout of 45.68% suggesting the nationalist PiS succeeded in mobilising its electorate as it heads to a general election this fall.

The party, in power since the 2015 general election, campaigned on a platform of generous social spending that saw its prime minister push hikes in pensions and child benefits through the Polish parliament.

"The PiS owes its success to a certain social inertia,"  veteran political scientist Jadwiga Staniszkis told the top-selling Fakt tabloid daily.

"People in rural areas didn't know much about the views of individual candidates and voted for the PiS due to its broad and generous public spending," she added.

"I'm very happy with the result of these elections,"  Gerard Schronski, a 60-year-old transportation company worker, told AFP in Warsaw on Monday.

"I support the policies of this government and I want us to have our own voice in the European Parliament," he added.

The PiS campaign was also marked by strong rhetoric against gay rights and a refusal to honour Jewish claims for the compensation of properties lost during the Holocaust.

The government has stoked tensions with the EU by introducing a string of controversial reforms that Brussels says pose a threat to judicial independence, the rule of law and ultimately to democracy.

Warsaw has since backed out of some of the legislation, but the opposition is still concerned that the clash with Brussels could pave the way to a "Polexit".

Jaroslaw Kaczynski has long been a fierce critic of the strong brand of EU federalism championed by the bloc's powerhouses Germany and France.

He is among a growing number of populist leaders in the EU advocating a reform agenda for the bloc that favours national sovereignty over further integration and federalism.

PiS Prime Minister Mateusz Morawiecki ruled out teaming up with France's far-right National Rally but said his party was "ready to talk" with Italian and Spanish anti-immigrant and ultra-nationalist parties in the European parliament.