England, Scotland and Wales use a closed-list party list system of PR (with the D'Hondt method), while Northern Ireland used the single transferable vote (STV).

The Liberal Democrats, who were in government in the UK with the Conservatives at the time, lost 10 of the 11 seats they were defending, and won just 7% of the popular vote.

Figures released in December 2014 showed that the Conservatives and UKIP each spent £2.96m on the campaign, the Liberal Democrats £1.5m, and the Labour Party approximately £1m.

The Electoral Commission performed a reallocation in keeping with the same procedures it used to allocate 72 MEPs; an extra Conservative MEP was allocated to the West Midlands constituency, based on the 2009 vote, and was enshrined in the European Union Act 2011 as an amendment of the European Parliamentary Elections Act 2002.

In December 2011, a 73rd member from the UK (Anthea McIntyre, Conservative) was allocated to England because of the implementation of the Treaty of Lisbon.

Labour, the Liberal Democrats and the BNP had a full slate of candidates in all the regions in Great Britain (i.e. excluding Northern Ireland).

(Elected in 2009 as British National Party) On 20 February, the Deputy Prime Minister Nick Clegg used his weekly phone-in show on LBC 97.3 to challenge the leader of the UK Independence Party, Nigel Farage, to a live public debate on the UK's membership of the European Union.

The second debate was held on BBC Two on 2 April in a special programme called The European Union: In or Out, moderated by David Dimbleby.

Farage was again seen as outperforming his rival, with a snap poll by YouGov showing 68% of people thought he did better in the debate compared to 27% for Clegg.

[41] The governing Conservative Party was pushed into third place for the first time at any European Parliament election, winning just 23.3% of the national vote share and losing 7 seats to fall to 19 overall, one behind Labour.

The Green Party of England and Wales saw its number of MEPs increase for the first time since 1999, winning a total of 3 seats.

[42] The Liberal Democrats, who were in coalition with the Conservatives at the time, lost ten of the eleven seats they were defending and won just 6.9% of the vote share nationally.