Campaigners against changing the way MPs are elected have claimed a "resounding" victory as the No camp gained an unassailable lead in the UK-wide referendum.

With 403 of 440 results declared, more than 11.4 million people had rejected a switch to the Alternative Vote, with 5.2 million in favour - a margin of around 69% to 31%.

Senior political figures on the No campaign said the scale of the victory meant it was not simply a vote against AV but a firm endorsement by the public of the first-past-the-post system.

The milestone was cheered at the conference centre in London's Docklands where politicians gathered to hear the results announced by the Electoral Commission. A majority in favour of the reform was registered in only eight of the areas declared so far.

"We've won," a delighted No to AV campaign spokesman said in the sparsely-attended hall - where supporters of each side gathered to listen to regional results being read out.

The rejection of AV, under which voters rank candidates in numerical order, was a further humiliation for Deputy Prime Minister Nick Clegg, for whom a referendum on voting reform was his main prize in negotiations to form a coalition last year.

But prominent Lib Dems insisted that, despite the setback on electoral reform and the party's disastrous showing in elections to English councils, the Scottish Parliament and Welsh Assembly, Mr Clegg's position was safe and the coalition would survive.

Liberal Democrat Cabinet minister Chris Huhne accepted that there would be no further attempt to introduce voting reform during this Parliament and that it was "over" for the Alternative Vote.

He appeared to leave the door open though for the Lib Dems to attempt to introduce some other, more proportional, system in the future, telling Sky News: "I think it is over for the Alternative Vote. I think it is very clear that the people have spoken, that the Alternative Vote is not a runner and we must respect that decision."

Nick Clegg described the no vote in the AV referendum as a "bitter blow". The overall turnout across the UK in the referendum was 42%, some 19.1 million votes, according to the provisional figures of the Electoral Commission.