The European Greens will hold US-style primary elections to select their candidates for the EU's top jobs at the next European elections.

At a press conference in Brussels on Thursday (16 May), the co-chairs of the European Greens, Monica Frassoni and Reinhard Butikofer, said party members and supporters would vote online in a pan-European election to select two candidates to spearhead their election campaign.

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Frassoni, an Italian former MEP, described the primary as "the kind of participatory tool that is vital to reconnect citizens to the European Union."

She added that it would "mobilise people for the European elections at an early stage that will also help to close the gap between citizens and EU institutions.”

Under the rules, candidates will need the support of at least five of the 33 different Green member parties across the EU's soon-to-be 28 member states, with the top six candidates then taking part in a series of hustings and debates in European capitals in November and December.

Voting is set to take place online all across Europe between January and February 2014.

Although the two candidates, which will include at least one woman, will front the campaign for the parliament elections, one will be nominated as the party's candidate for the European Commission presidency.

While the Greens are the first European political party to launch an open primary, the other leading party groups are also expected to unveil plans to increase voter involvement in the European elections.

With a year to go until the poll, political leaders fear that another low turnout could undermine the democratic legitimacy of the EU institutions, and particularly the parliament.

In the 30 years between the first direct elections in 1979 and the last elections in 2009, turnout fell from over 60 percent to 43 percent.

For their part, EU officials and the party groups are anxious to ensure that the campaigns are not reduced to 27 separate national campaigns across the bloc.

The main pan-European parties are expected to publish their election manifestos at the start of 2014.

The four major groups have also indicated that they will present candidates for the European Commission presidency.

A possible runner from the centre-right EPP, the largest group in parliament, is Polish Prime Minister Donald Tusk.

Danish Prime Minister Helle Thorning-Schmidt and Parliament President Martin Schulz have been touted as candidates for the centre-left Socialists and Democrats.

Meanwhile, Nato Secretary General Anders Fogh Rasmussen could be the front man for the Liberal Alde faction.