Deputy Prime Minister Nick Clegg insisted today that the Conservative-Liberal Democrat coalition Government was not a "one-off accident" but marked a permanent change in British politics.
In an interview with The Guardian, the Lib Dem leader suggested that further coalitions were likely and that majority Labour or Tory administrations were a thing of the past.
"We are living in a society where the old duopoly of the parties has broken down for good," he said. "I don't think this is a one-off accident."
Mr Clegg is in charge of electoral reform for the coalition and is trying to replace the first-past-the-post voting system with the alternative vote (AV) - a move which is likely to further increase Lib Dem representation at Westminster.
A referendum on the change, in which Tory Prime Minister David Cameron will argue to retain the status quo, is planned for May 5.
But Mr Clegg said the coalition, arising from the failure of any party to secure an outright majority in the general election, was the consequence of what had been happening "for years, which is a loosening of the old tribal ties between the old parties and their supporters.
"Something very, very big is happening in politics."
He added: "I think what we are entering into is a permanent move to greater pluralism, diversity, and fluidity in politics that does not settle down to one associated pattern between parties."
The Deputy Prime Minister accused Labour, who regarded the coalition as "an unnatural act", of failing to recognise a "profound" shift in politics. There was "a deep change in the way people regard politics psychologically", he said.
The adoption of AV at the next general election, planned for May 2015, would finally break the "deathly grip of a first-past-the-post electoral system that made sense in the 50s when duopoly politics was its height".
Aware that most Tories were strongly opposed to AV, he insisted: "I think the Conservatives will look at it and realise that because the old patterns of voting are not cast in stone, the system is as good or as bad for any other party."
Drawing on his experience of the coalition so far, Mr Clegg said government benefited from the degree of openness needed within the partnership, contrasting it with the "collective bile" of the Labour leadership candidates.
Of the alliance, he said: "What we have learned about each other most of all is that if you are in a coalition you have just got to be constantly open, pragmatic and level-headed about how you make progress together."