The British parliament has cleared the way for a referendum to be held in May on changing the way MPs are elected, a vote which will divide the ruling coalition partners.
The Conservatives want to maintain the present first-past-the-post system, but the Liberal Democrat partners have long campaigned for a switch to a model that is more favourable to smaller parties.
Late last night the government won a 68-vote majority against a proposal by the House of Lords, to require a 40% turnout threshold for the referendum to be binding.
Britons will be asked if they want to move to an Alternative Vote (AV) framework where voters choose candidates in order of preference.
If there is no majority winner, the second preference votes of the candidate with the fewest votes overall are redistributed. This process continues until a candidate achieves more than 50% of the overall vote.
The referendum was one of the key agreements extracted by the Lib Dems as the price for entering a coalition last May, although it falls short of their ultimate goal of a full proportional system.
Failure to win the referendum vote is likely to increase pressure on party leader Nick Clegg who has been criticised by party activists for ceding too much ground to the Conservatives.
Support for the Lib Dems has slumped since the election, with many former supporters angry with the party after it dropped its opposition to higher fees for university students.
The referendum on 5 May will coincide with local elections in parts of England and voting for the Scottish parliament and devolved assemblies in Wales and Northern Ireland.
Holding the votes on the same day will cut costs and is likely to boost turn-out, a move welcomed by the ‘Yes’ campaign.
The proposals, bound up with disputed measures to cut the number of MPs to 600 from 650, had been debated for several weeks in parliament, with a number of all-night sessions held.
This week was the deadline for approval to allow enough time to prepare the May referendum.
