AMSTERDAM (Reuters) - Dutch mainstream, EU-supporting political parties made gains in the first test of the European Parliament election, according to an exit poll that showed a surprise Labour victory and a weak showing for eurosceptics in the Netherlands.

Frans Timmermans of the Party of European Socialists (PES) reacts during a press point after a debate which is broadcast live across Europe from the European Parliament in Brussels, ahead of the May 23-26 elections for EU lawmakers, in Brussels, Belgium May 15, 2019. REUTERS/Francois Walschaerts

The Netherlands and Britain were the first of 28 member states to vote in the EU election on Thursday. Irish and Czech voters were casting their ballots on Friday and the other 24 countries were due to vote on Sunday.

In Britain, where results will not be released until Sunday, opinion polls showed Prime Minister Theresa May’s Conservative Party hemorrhaging support to veteran eurosceptic Nigel Farage’s newly formed Brexit Party. May said on Friday she would resign as party leader on June 7 amid deep paralysis on Brexit.

Dutchman Frans Timmermans, a vice president of the executive European Commission who is now the leading center-left candidate to head that body, defied opinion polls with a surprise victory for his Labour Party, the Ipsos exit poll showed.

The chaotic political situation in Britain may have influenced voters in the Netherlands, which is highly exposed economically to Brexit. Turnout hit a three-decade high for an EU election of 41%, up from 37% in 2014.

Mainstream Dutch parties that support the EU took 70% of the vote, 3% more than they did five years ago, the Ipsos poll showed. Anti-EU parties slipped nearly 1% to 19%, according to the poll, which had a 2% margin of error.

Political pundits cautioned not to read too much into the Dutch result, saying there may have been a domestic “Timmermans effect” that drew out supporters for a home-team candidate with a high profile.

“IDIOSYNCRATIC” RESULT

Cas Mudde, a professor of international affairs at the University of Georgia in the United States, said he was “sceptical about people reading European trends into” the Dutch vote. “It’s idiosyncratic and doesn’t mean anything for other Social Democratic parties.”

The Forum for Democracy of Dutch nationalist Thierry Baudet, which had been polling neck and neck in first place alongside the conservatives of Prime Minister Mark Rutte, ended fourth. Geert Wilders’ anti-immigration Freedom Party fell to 4%, its worst showing since it was established in 2006.

No opinion poll before the vote had put Labour anywhere better than third place, but it ended first with 18 percent, three points ahead of Rutte’s ruling center-right VVD.

Baudet may have lost strong momentum in the final week of campaigning after publishing a book review that questioned whether women can both work and have children, and retweeting a video that was hosted by a German white supremacist group.

In Britain, a YouGov poll on Wednesday had put support for Farage’s Brexit Party, which is campaigning for Britain to leave the European Union immediately and with no divorce deal if necessary, at 37%. May’s Conservatives, deeply divided over Brexit, had just 7%.

In France, Marine Le Pen’s eurosceptic National Rally leads opinion polls, slightly ahead of President Emmanuel Macron’s strongly pro-EU Republic On the Move party, according to a survey published by Les Echos newspaper on Thursday.

In Germany, Chancellor Angela Merkel’s conservatives are expected to remain the largest party, with the far-right Alternative for Germany seen only in fourth place at 12%.

Italy’s far-right ruling League party, led by Deputy Prime Minister and Interior Minister Matteo Salvini, is seen remaining the country’s largest.