Q+A - How do the elections work?

LONDON (Reuters) - The election on May 6 may fail to produce a clear-cut winner, with the three largest parties relatively close in the polls.

The quirks of the system mean Labour could remain the largest party in parliament even if it comes third in terms of percentage share of the national vote.

Below are answers to some key questions about the upcoming elections.

Q. What are people voting for?

A. In a parliamentary election, people in each voting area or constituency around Britain choose one member of parliament (MP) to represent their constituency in the House of Commons, the lower chamber of parliament.

The 2010 general election will use new constituency boundaries, meaning that after the general election there will be 650 seats in the Commons (lower house) representing constituencies across England, Wales, Scotland and Northern Ireland. At present there are 646 seats.

Q. How is an MP elected?

A. Each eligible voter has one vote in their local constituency, and the candidate with the most votes becomes the MP for that area. Candidates do not need an overall majority to win. This voting system is called "first past the post."

Q: Who forms the government?

A: The political party with the most MPs usually forms the government -- though two or more parties with a combined majority of MPs may form a coalition government.

Q. What is a hung parliament?

A. A hung parliament is one in which no party has more than half of MPs in the House of Commons, meaning it needs the support of other parties to pass legislation.

The opposition Conservatives are favourites to win the 2010 election, according to opinion polls, but in order to obtain an overall majority they would require a swing of 6.9 percent in the national vote from ruling Labour to the Conservatives. This would be a bigger swing than in any election since 1950, except 1997.

Q. How is the prime minister chosen?

A. The leader of the party with the largest number of votes usually becomes prime minister.

The incumbent, Gordon Brown, became prime minister in 2007 after his predecessor Tony Blair resigned in mid-term and Brown succeeded him as leader of the Labour Party. This will be the first time Brown has led the party into a general election.

Q. How often are general elections held?

A: There has to be a general election at least every five years. The prime minister decides when to call an election. The current Labour government has been in power since May 5, 2005.

Q: Who can vote?

A: British citizens, and Commonwealth and Irish citizens living in the UK, who are over 18 years old on polling day can vote, as long as they are on the electoral register.

Members of the House of Lords, which is the unelected upper chamber of parliament, as well as convicted prisoners and anyone guilty in the previous five years of corrupt or illegal election practices, cannot vote.

(Editing by Sonya Hepinstall)