There are 31 parties putting up candidates for the European elections in Britain on 22 May. Some are well known, others less so. Here's a guide to all of them, beginning with those who already have a Member of the European Parliament:
Prime Minister and Conservative leader David Cameron said he had a track record of delivering on Europe at the launch of his party's campaign. On the party website, the Conservatives are focusing on their pledge to hold a referendum in 2017. Candidates: Fielding candidates in every region of Britain. 2009 result: 27.7% of votes, 25 MEPs elected
UK Independence Party
UKIP leader Nigel Farage predicted "an earthquake" in politics at his campaign launch. The party, which wants the UK to leave the EU, is focusing on its website on the impact of being in the European Union on control of the UK's borders. Candidates: Fielding a full slate of candidates in every region of Britain. 2009 results: 16.5% of votes, 13 MEPs elected
Ed Miliband promised to campaign for change within the European union as he launched his party's election campaign. On its party website, Labour says its MEPs will put "jobs and growth" at the heart of the EU. Candidates: Fielding candidates in every region of Britain. 2009 result: 15.7% of votes, 13 MEPs elected
Nick Clegg pitted his party's "optimism and openness" against the "fears and falsehoods" of "isolationists" at the launch of the Liberal Democrat campaign for the European elections. On the party website, the Lib Dems say the "fight is on" to keep the UK in the EU. Candidates: Fielding candidates in every region of Britain. 2009 result: 13.7% of votes, 11 MEPs elected
Green Party of England and Wales
At the launch of the Green Party of England and Wales campaign, leader Natalie Bennett said the party would continue to "make a real difference" on issues like bankers' bonuses and fishing policy. On its party website, the Greens say European policy "does not need to be a shouting match" between extremes. Candidates: Fielding candidates in England and Wales. 2009 results: 8.6% of votes, two MEPs elected.
Scottish Green Party
The Scottish Green Party is hoping to beat the Liberal Democrats to sixth place in Scotland, claiming the constituency's final available seat in the European Parliament. The party backs a Yes vote in September's independence referendum and is campaigning for more power to be handed to local communities and better public services, according to their website. Candidates: Scotland only. 2009 result: 7.31% of vote, no MEPs elected.
British National Party
The BNP wants the UK to withdraw from the EU, while maintaining trade-based co-operation with other European countries. On its website, the party says it is the true patriots of British politics. Candidates: Fielding candidates in every region of Britain. 2009 results: 6.2% of vote, two MEPs elected.
Scottish National Party
The SNP promised to "ensure that Scotland's interests are always defended" in Brussels at its campaign launch. On its party website, it says Scotland needs a "seat at the top table" to make its voice heard. Candidates: Fielding candidates in Scotland only. 2009 result: 29.1% of votes in Scotland, two MEPs elected.
Skilled migrants from other countries should be targeted to move to Wales, Plaid Cymru said as it launched its manifesto. On its party website, it says it will campaign for Welsh to be given the same status as other languages within the EU. Candidates: Fielding candidates in Wales only. 2009 result: 18.5% of votes in Wales, one MEP elected.
Here are the parties hoping to secure their first MEPs, listed in order of the number of candidates they are fielding:
The English Democrats launched their campaign pledging to "look after English interests" and arguing it was unfair to charge English people for prescription charges and tuition fees when these are free for residents elsewhere in the UK. On its party website, it points out the launch took place on site of the 1381 Peasants' Revolt. Candidates: Fielding candidates in every region of England.
An independence from Europe
The party is pledging to take the UK out of the European Union without a referendum, to scrap VAT and build stronger links with the Commonwealth. It describes itself as an inclusive, democratic, Euro-realist, party on its website. Candidates: Fielding candidates in every region of England
No2EU - Yes to Democracy
The party wants to hold a referendum on EU membership as a prelude to leaving the union. On its party website, it says it opposes privatisation and campaigns for workers' rights and decent public services. Candidates: Fielding candidates in the east and north-west of England, London, the West Midlands, Yorkshire and the Humber, Wales, and Scotland.
Christian Peoples Alliance
On its website, the party says the EU must be reformed to reflect the "Christian vision" of its founders and unless this happens, the UK should seek to leave. Candidates: Fielding candidates in the east and south-east of England, and London.
Socialist Party of Great Britain
On its website, the party says it will be campaigning for common, democratic ownership of public services, the abolition of property rights and an end to inequality. Candidates: Fielding candidates in south-east England and Wales only.
On its website, the party promises to promote a "robust and confrontational" message about the need to leave the European Union, end immigration and put British workers first. Candidates: Fielding candidates in Scotland and Wales only.
The party supports the UK's continued membership of the the European Union, which it says is a "force for peace", but urges the EU to be more pro-active. On its website, it also calls for a living wage and all foreign troops to be withdrawn from Afghanistan. Candidates: Fielding candidates in south-east England only.
The party is campaigning for EU subsidies to be redirected away from livestock and fisheries farming into plant-based agriculture. On its website, it lists its other objectives including promoting healthy, plant-based lifestyle initiatives through public health and education campaigns. Candidates: Fielding candidates in London only.
On its party website, Communities United says it is campaigning for reform of council tax and business rates and a university education for all. Candidates: Fielding candidates in London only
The party is vowing to give London a "strong voice" within the EU. On its website, it commits to aligning its MEPs with the European People's Party, the largest grouping in the European Parliament. Candidates: Fielding candidates in London only
National Health Action Party
The NHS should be exempt from a proposed new free trade treaty between the European Union and the United States and food regulation should be strengthened, the party says on its website. Candidates: Fielding candidates in London only.
National Liberal Party
If elected, the party says its MEPs will consult constituents through social media and petitions before deciding how to vote on key issues. On its party website, it says its MEPs will also donate part of their salaries to good causes. Candidates: Fielding candidates in London only.
Socialist Equality Party
The European Union should be replaced by a United Socialist States of Europe, the party says, with "workers' governments" and an end to the "age of austerity". On its party website, it says it is aligned with its sister party in Germany, Partei Für Soziale Gleichheit. Candidates: Fielding candidates in north-west England only
We Demand a Referendum Now Party
On its party website, the Europeans Party says it is committed to promoting the UK's national interest within the EU and fighting "prejudice and discrimination" based upon nationality. Candidates: Fielding candidates in London only.
On its party website, the Harmony Party describes itself as "ready and willing to remedy the inequalities of the current system of governance where the UK and Europe are concerned." It is fielding candidates under the slogan "zero immigration, anti-EU, pro-jobs". Candidates: Standing in the East Midlands, West Midlands, London, and south-east England only.
Socialist Labour Party
The party, led by Arthur Scargill, advocates withdrawal from the EU so the UK can "regain control of its economy, sovereignty and political power". On its party website, Mr Scargill says British farmers are "being paid not to produce food" at a time of worldwide shortages. Candidates: Fielding candidates in Wales only.
Liberty GB Party
On its website, the party says it is campaigning for withdrawal from the EU, the repeal of existing EU laws, the abolition of the Human Rights Act and legislative guarantees for freedom of speech. Candidates: Fielding candidates in south-east England only.
All institutions, including the EU, should be more transparent and accountable, the party believes. It also wants EU data retention and intellectual property rights directives to be repealed. On its party website, it claims there "is more to life than Nick vs Nigel". Candidates: Fielding candidates in north-west England only.
On its party website, Yorkshire First says it is campaigning for a stronger voice for the region in national and European politics and more devolution, including a Parliament for Yorkshire. Candidates: Fielding candidates in Yorkshire and the Humber only.
On its website, YOURvoice is pledging to deliver "a better democracy". It states that constituents will be able to vote online to directly influence how its MEPs represent them in the European Parliament. Candidates: Fielding candidates in south-east England only.
The party, the brainchild of bus driver Jean-Louis Pascual, campaigns for an end to injustice and greater educational opportunities - as well as increasing knowledge of the Romans' contribution to modern Britain. It does not have a website. Candidates: Fielding one candidate in south-east England only.
A separate system is in place in Northern Ireland. More details on the candidates.
Here is a full list of candidates standing across the UK.