Peers have warned the size of the House of Lords will hit 1,000 if political parties fail to back their plans to cut numbers.

The number of peers should be cut by a quarter to 600 and then capped at that level, a committee has recommended.

Parties are being asked to sign up to a “two out, one in” system to hit the new level in just over a decade.

New peers would serve a maximum of 15 years under the recommendations from the Lord Speaker’s committee.

The proposals come after criticism over the bloated size of the chamber and the scale of expenses claimed by some peers who fail to play an active role in the Lords.

Reforms can be carried out without legislation but will need the backing of Prime Minister Theresa May and co-operation from political parties, the committee said.

About 35 appointments have been made a year since 1997 and the average life expectancy of new members is 25 years.

In the long-term that would mean “the number of life peers will settle at about 875 which, together with 92 hereditary peers and 26 bishops, would give a total membership of nearly 1,000”.

Committee members said they were “in persuasion mode” and described the recommendations as “our best shot in a generation” of securing change.

Chairman Lord Burns said: “The real danger of the present situation is that the House size will continue to grow.”

Under the plans, the chamber would reflect general election results.