The government's plan to introduce five-year fixed-term parliaments will make politicians less accountable to voters, peers have warned.
The Lords Constitution Committee said the gap between elections, with the next due in 2015, would be "too long".
The coalition argues that fixed-term parliaments will make it impossible for the ruling party to choose polling dates for their own advantage.
But the peers said they remained "unconvinced" by this claim.
The coalition government wants to change the law so UK general elections are held on a fixed, five-year cycle.
Currently the prime minister can choose the date of the next general election at any time within a five-year period.
But the committee said the government's reform plans - outlined in the Fixed-term Parliaments Bill - owed "more to short-term considerations" of maintaining the Conservative-Liberal Democrat coalition in power than "enduring constitutional principles or sustained public demand".
Its report also said fixing the length of parliaments to five years would mean "less frequent elections and make the legislature less accountable not more".
It argued there have been 18 general elections since 1945, with an average parliament lasting three years and 10 months. Under a system of fixed five-year terms there would have been four fewer elections in that period, the committee added.
The report went on on to say that the term should be set at four years, as is the case for the devolved administrations in Scotland, Wales and Northern Ireland.
This follows a failed attempt by Plaid Cymru, Labour and the Scottish National Party to alter the plans to this effect last month.
The report said the five-year proposal was "inconsistent with the government's stated aim of making the legislature more accountable, inconsistent with existing constitutional practice and inconsistent with the practices of the devolved institutions and the clear majority of international legislatures".
Fixed-term parliaments could reduce democratic accountability by lowering the chance of an early election following an "exceptional event such as a drastic change in the make-up of a government, if a government was no longer able to govern effectively or if there is a change of prime minister".
The committee' chairman, Labour's Baroness Jay, said: "In our view the government have failed to make the case for such a significant constitutional change and undertook no consultation or pre-legislative scrutiny before they bought the legislation to Parliament. That is extremely regrettable."
The coalition, for whom Deputy Prime Minister Nick Clegg is leading a programme of constitutional reform, says fixed-term parliaments will bring greater stability to UK politics.
In October, Mr Clegg told the committee: "It's a combination of providing a length of time with which people are familiar and which allows governments at least maybe four of those five years... to get on with governing properly for the benefit of the country, combined with taking away from the executive this ability to capriciously time the election for nothing more than political self-interest."