David Cameron has defended his plan for a fixed-term parliament
David Cameron has said his government's plans for fixed term parliaments are a "huge" and "good" change - amid concern some changes amount to a "stitch up".
He said he was the first British PM to give up power over when an election was called and that should be "welcome".
But Labour and some of his own MPs have attacked plans to allow 55% of MPs to vote for Parliament to be dissolved.
Tory Christopher Chope said it may be a "recipe for anarchy", as 51% of MPs could back a no-confidence vote.
The Lib Dem-Tory coalition deal builds on the Lib Dem manifesto commitment to fixed-term parliaments. It commits the government to a five-year term - rather than, as currently, allowing the prime minister to choose when to call an election within a five-year period.
But concerns have been raised about a clause in the document which says the legislation "will also provide for dissolution if 55% or more of the House votes in favour". The threshold for a no-confidence vote - which in recent times has led to an election being called - is 50% plus one MP.
Three Conservative MPs - Richard Ottoway, Christopher Chope and Charles Walker have raised concerns about it, saying they believe it could be unconstitutional - as it would mean a government that did not have the support of a majority of MPs - 51% - would not fall.
Mr Chope told the BBC: "It could mean in practice that if the present government was to lose its majority in Parliament, and wasn't able to operate as a minority government because it didn't enjoy the confidence of a sufficient number of MPs ... it would be able to carry on. But that would be basically a recipe for anarchy, because it would mean that the government wouldn't have a majority."
Mr Ottoway told the BBC Conservative MPs "desperately need some clarification pretty quickly". He said he was "confused" as to why the proposal was needed in the first place. He said a senior minister needed to consult and explain the situation to backbenchers, rather than the "constitutional incoherence that's going on at the moment".
And Labour figures such as David Blunkett, Lord Adonis, Jack Straw and Lord Falconer have hit out at the plans with Mr Straw condemning it as "completely undemocratic and totally unworkable" and Mr Blunkett describing it as a "stitch-up".
Speaking on a visit to the Scottish Parliament, Mr Cameron said the changes would provide a "strong and stable government" over the next five years and should be "welcome".
He said: "I'm the first prime minister in British history to give up the right unilaterally to ask the Queen for a dissolution of Parliament. This is a huge change in our system, it is a big giving up of power. Others have talked about it, people have written pamphlets and made speeches about fixed-term parliaments, I have made that change. It's a big change and it is a good change."
He added: "Here in the Scottish Parliament you actually require a vote of 66% of MSPs to change the arrangements - we have argued for the case of 55% - but clearly if you want a fixed term parliament, you have to have a mechanism to deliver it. Obviously that is a mechanism that can be debated in the House of Commons, it can be discussed, but I believe that it is a good arrangement to give us strong and stable government."
'Not a monstrosity'
Former Lib Dem MP David Howarth, a legal academic who drew up the original Lib Dem plans for a fixed-term parliament, told the BBC that in other countries with fixed-term parliaments, if a government lost a vote of confidence the parties would have to try to work out a new government within the fixed term, he said.
He said critics had got "entirely the wrong end of the stick" adding: "This dissolution vote, the 55% for a dissolution, is not the same as, for a vote of confidence."
There is also some disagreement among constitutional experts. Professor Peter Hennessy, of Queen Mary University of London University, told the BBC it looked like "very very iffy politics indeed" but Professor Robert Hazell, director of the Constitution Unit think tank, told the BBC: "It's not some constitutional monstrosity as people have supposed to have a slightly higher threshold. We already do this in Scotland."
He added that if First Minister Alex Salmond lost a no-confidence motion, he would have to resign - and the same thing would happen in Westminster.
The Conservatives currently have 306 out of 649 MPs - a 47% share.
One seat, Thirsk and Malton, is empty, pending a by-election on 27 May, while Sinn Fein's five MPs have not taken the oath of allegiance allowing them to sit in Parliament.
It would be impossible for opponents, even if fully united, to muster the 55% needed to dissolve Parliament, unless at least 16 Tories rebelled against their party leadership.
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