Above all, FPTP is not very representative, disproportionately rewarding parties whose support is geographically concentrated.

ECONOMIST: Constitutional reform in Britain

FPTP, which Mr Curtice thinks costs them 80 seats, because of the way their vote is spread across the country.

ECONOMIST: An alternative way of voting

Historically, FPTP has favoured the election of majority governments, able to defend a clear programme or face ejection at the next election.

ECONOMIST: Constitutional reform in Britain

Most Tory MPs (and quite a few Labour ones) oppose changing FPTP, but Lib Dems hate it because it punishes smaller parties.

ECONOMIST: Voting reform

But because Conservatives fear that they would not win an outright majority in a proportional representation (PR) system, the Lib Dems could secure only a more modest prize: a referendum on keeping FPTP or adopting the alternative vote (AV).

ECONOMIST: Constitutional reform in Britain

The majority of MPs (80 to 85%) would continue to be elected on an individual constituency basis, with the remainder elected on a corrective top-up basis which would significantly reduce the disproportionality and the geographical divisiveness which are inherent in FPTP.

BBC: The Jenkins Report: What it says

Constitutional Reform Minister Mark Harper said the coalition wanted to hold the plebiscite on replacing first-past-the-post (FPTP) with the alternative vote (AV) system at an "early opportunity" so voters would know what system they would be using for the 2015 general election.

BBC: Parliamentary Voting Bill part one

At the general election Britain's third party picked up nearly a quarter of all votes but fewer than one in ten seats: small wonder that the Lib Dems loathe FPTP, and made a referendum on ditching it a key demand before joining the Tories in a coalition.

ECONOMIST: Constitutional reform in Britain