Nick Clegg will ask MPs to back a move to fixed-term, five-year parliaments today amid warnings the legislation is rushed and could open Parliament to legal challenge.
The Deputy Prime Minister will hail the move to strip prime ministers of the power to pick election dates for party advantage as a "profound" reform.
But an influential committee of MPs last week raised a number of concerns about the Fixed-Term Parliaments Bill - which faces its first Commons hurdle this afternoon.
At present, a prime minister can ask the Queen to dissolve Parliament at any time within five years of the previous general election.
Under the Bill, general elections would take place on the first Thursday in May every five years from the next time voters go to the polls - which would be May 7, 2015.
Parliament would be dissolved early if no government could be formed within 14 days of a simple majority vote of no confidence, or if two-thirds of MPs voted to trigger a general election.
The latter threshold was raised after a political outcry over initial plans to set it at 55%.
In a hastily-prepared report, the cross-party Political and Constitutional Reform Committee welcomed the reforms but attacked the Bill's "unnecessarily" accelerated timetable.
It also highlighted concerns from the House of Commons' top official that Parliament could be left open to legal challenge and suggestions four-year terms could be more appropriate.
Clerk of the House Malcolm Jack told the committee that provisions in the Bill, which would require the Speaker to issue a certificate declaring that the dissolution requirements had been met, could lead to scrutiny by the courts.
He suggested using standing orders, rather than the statute book, to ensure the courts could not interfere in Parliament's internal workings.
Ahead of the debate, Mr Clegg said: "Establishing parliaments of fixed-terms is a straightforward, but fundamental, change in our politics. It is a simple constitutional innovation, but one that will have a profound effect.
"For the first time in our history, the timing of general elections will not be a plaything of governments. Prime ministers will no longer have the power to go to the polls at a time of their own choosing.
"Instead, there will be greater stability in our political system and people will know exactly how long a parliament can be expected to last.
"There may be exceptional circumstances in which it would not be appropriate for Parliament to continue to run for its full term.
"When there is a need to seek an earlier dissolution, that will be for the House - not the Government - to decide."Reuse content