A referendum on changing the way MPs are elected will be held by October next year under Government plans passed by the Commons.
Despite strong opposition from the Tories and vocal criticism from some Labour backbenchers, MPs voted 365 to 187, a Government majority of 178, to ask the British people to decide whether the traditional first-past-the-post system should be scrapped in the biggest shake-up of the election system in generations.
But the Government faces an uphill battle to force the changes through Parliament with the prospect of stiff resistance in the House of Lords and time running out before the general election.
Gordon Brown's proposal would allow people to choose whether to adopt an Alternative Vote (AV) system which would allow them to rank candidates in order of preference.
Critics accused Mr Brown of a cynical ploy in order to win the support of Liberal Democrat MPs in the event of a hung parliament at the next general election. The Government also came under fire over the £80 million cost of the plebiscite at a time when public spending is under intense pressure due to the record budget deficit.
The proposals came in committee stage amendments to the Constitutional Reform and Governance Bill tabled by Justice Secretary Jack Straw.
He told MPs the expenses scandal had led to a "crisis of confidence in our political system and in our politicians on a scale which none of us have witnessed in our political lifetime".
Mr Straw said the AV system was not proportional representation.
The Liberal Democrats wanted to see the more radical single-transferable vote (STV) as a referendum option but said AV was "a small gain but a gain worth having".
A Liberal Democrat bid to include STV as the referendum option, rather than AV, was rejected by 476 votes to 69, a Government majority of 407.
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