FILE PHOTO: European Competition Commissioner Margrethe Vestager attends the weekly College of Commissioners meeting in Brussels, Belgium, Februray 6, 2019. REUTERS/Yves Herman/File Photo

BRUSSELS (Reuters) - The European Union’s top antitrust regulator Margrethe Vestager on Thursday joined the fray for the presidency of the next European Commission, a post up for grab after EU parliamentary elections in May 23-26.

A former finance minister of Denmark, Vestager has gained a reputation as a tough enforcer of the bloc’s competition rules, slapping big fines on large corporations, like Google and Apple, and blocking a rail merger between Germany’s Siemens and France’s Alstom despite Berlin and Paris’ pressure to authorize the deal.

EU Competition Commissioner, Vestager was put forward in a team of lead candidates by the European liberal party, alongside six other prominent politicians from the centrist group, which include Belgium’s former prime minister Guy Verhofstadt and the EU transport commissioner Violeta Bulc.

Polls show the liberals will be the third force in the next European Parliament, where the influence of the two traditional leading groups, the conservatives and the socialists, is set to dwindle.

With the expected rise of eurosceptic parties, the liberals could play a crucial role to form a pro-EU majority in the next assembly, giving Vestager and other candidates from the group a chance to win the commission’s top job, which is now held by Luxembourg’s former prime minister Jean-Claude Juncker.

Under an election method backed by the EU parliament and some EU states, the president of the EU executive should be the leading candidate of the party that wins the European elections.

Polls show that the conservatives, whose candidate is German lawmaker Manfred Weber, are set to remain the main grouping in the next parliament.

But to win a majority of the seats, they will need the backing of their traditional socialist allies, whose candidate is EU commission’s vice-president Frans Timmermans, and other pro-EU parties, including the liberals.