Voters from across the European Union will be electing a new European Parliament in June - the first election since the EU enlarged in 2007, with the accession of Bulgaria and Romania.
Nearly all the 736 winning MEPs will join a political group within the European Parliament - only a few sit as independents.
Here, leaders of the
political groups in the outgoing parliament
explain why, in their view, people should turn out to vote.
ALDE GROUP, GRAHAM WATSON
"The importance to liberal democrats is to try to give us a stronger liberal democratic representation at European level, to make sure the European Union works on behalf of its citizens."
The Alliance of Liberals and Democrats for Europe holds 100 seats in the outgoing parliament. Mr Watson's constituency is in south-west England.
EPP-ED GROUP, JOSEPH DAUL
"For us the European elections are very very important because the centre-right leads in the majority of European Union countries and therefore leads the economic policy decisions across the Union."
The European People's Party (Christian Democrats) and European Democrats (centre-right) hold 288 seats in the outgoing parliament. Mr Daul's constituency is in eastern France.
GREENS/EFA GROUP, MONICA FRASSONI
"It is very important that electors and voters understand that they have to go to vote, because this is not peanuts... like going to vote for an assembly that simply talks. Here there is real power."
The Greens/European Free Alliance (Greens and regionalists/nationalists) has 43 seats in the outgoing parliament. Ms Frassoni represents north-western Italy.
GUE/NGL GROUP, FRANCIS WURTZ
"What is at stake for these elections is a chance to put to an end the liberal orientation of the European Union ... The financial, economic and social crisis of the last few months only accentuates the need for change in the European Union."
French Communist Francis Wurtz leads the Confederal Group of the United Left - Nordic Green Left (far left). The group has 41 MEPs.
INDEPENDENCE/DEMOCRACY GROUP, NIGEL FARAGE
"We've got a chance here - where there's no wasted vote - to try to actually say what we think, and what UKIP's going to try and do is to turn those elections on 4 June into the referendum that we never had."
The Independence and Democracy Group (Eurosceptics) has 22 seats in the outgoing parliament. Eight are from Mr Farage's UK Independence Party.
PARTY OF EUROPEAN SOCIALISTS, MARTIN SCHULZ
"Growth, more jobs and decent salaries for ordinary people. That's what we want to see in member states and in Europe. Therefore people can make a choice between us and the right wing."
The Party of European Socialists holds 217 seats in the outgoing parliament. Martin Schulz represents a constituency in western Germany.
UEN GROUP, BRIAN CROWLEY
"Our group is the fourth biggest within the parliament. It's holding the balance of power between the bigger groups, the left and the right divide, so it gives you a certain amount of power."
The Union for Europe of the Nations (right-wing anti-federalists) holds 44 of the 785 seats in the outgoing parliament. Mr Crowley represents the Ireland South constituency.