By Robin Emmott
BRUSSELS (Reuters) - The center right has extended its lead over the center left in the race for dominance in the European Parliament elections this week, a poll showed on Tuesday, but both sides are expected to fiercely contest the presidency of the European Commission.
The European People's Party (EPP) will take 217 seats in the May 22-25 vote, a five-seat improvement on a week ago, according to an analysis of national surveys by PollWatch 2014, its final forecast before polls open.
Meanwhile, the center-left Socialists and Democrats (S&D) have lost ground over the past week. That puts the EPP 16 seats ahead of the center left.
According to the survey, the center right, the center left, the Liberals and the Greens - Europe's four mainstream groups - will take 69.5 percent of the 751 seats in the parliament.
But a quarter of seats look likely to be won by anti-EU or protest parties on the far right and far left, almost double their standing at the last election in 2009, reflecting frustration with high unemployment and low economic growth.
Under new EU rules, the party that wins the election is best placed to have its top candidate become the president of the European Commission, one of Brussels' most powerful jobs, with influence over Europe's 500 million citizens.
While the EPP, which groups parties such as Spain's People's Party and Germany's CDU, may beat the Socialists in the vote, political analysts see the Socialists as better placed to secure allegiances with other parties on the left.
Since the nominee for Commission president must be approved by parliamentary majority, the Socialists may argue that their candidate has greater legitimacy than the center-right EPP's.
The S&D group includes parties such as Britain's Labour and France's Socialists.
The nomination for Commission president will be made by EU leaders, who are required to "take into account" the results of the election in making their choice.
The poll forecasts that if the far right forms an alliance that included France's National Front and Geert Wilders' Party for Freedom in the Netherlands, it would win enough seats to form a group, meaning access to EU funds and greater influence.
The UK Independence Party (UKIP), which wants Britain to leave the European Union, could lead another anti-EU group.
For the Commission presidency race, the EPP has chosen Jean-Claude Juncker, 59, the former prime minister of Luxembourg and a central broker during the euro zone debt crisis.
The Socialists are backing Germany's Martin Schulz, 58, the current head of the European Parliament and a campaigner for more money to be spent helping young people get jobs.
The Alliance of Liberals and Democrats, known as ALDE, have chosen former Belgian Prime Minister Guy Verhofstadt as their candidate for Commission president. But PollWatch's latest survey sees the Liberals taking just 59 seats.
(Editing by Alison Williams)