WARSAW, May 26 (Reuters) - Poland's ruling Law and Justice party (PiS) came out narrowly ahead in Sunday's European Parliament vote, seen as test of the party's nationalist, eurosceptic platform before a national election later in the year.
An exit poll by pollster IPSOS showed PiS winning 42.4% of votes, up from 31.8% in the EU ballot five years ago and 37.6% during Poland's 2015 parliamentary election.
The opposition European Coalition, comprising the Civic Platform formerly led by European Council President Donald Tusk and a group of leftist and rural politicians, scored second with 39.1%.
If confirmed by official results, the strong showing by PiS will bolster a growing chorus of populists in Europe that share the broad goal of returning power to EU member states.
Voter turnout stood at 43%, a record high for a European election in Poland, following an acrimonious campaign dominated by issues such as gay rights, the legacy of the Holocaust in Poland, and the role of the Catholic Church in public life.
PiS had framed the European ballot as a battle against western liberal ideals which it says threaten the traditional way of life in Poland, a staunchly Catholic country.
Another term in office for PiS following the national vote in October or November could deepen Poland's isolation in the European Union amid criticism that the party is tilting towards authoritarian rule.
"We have to remember, the decisive battle for the future of our homeland will take place in the autumn," PiS leader Jaroslaw Kaczynski told party supporters after exit poll results were published. (Reporting by Pawel Florkiewicz and Agnieszka Barteczko Editing by David Holmes)