Former Conservative justice secretary Alex Chalk has said the justice system should not be locking up “everyone we’re cross with” as longer custodial sentences are expensive.

The prison population reached a new record high of 88,521 people on Friday and has risen by more than 1,000 people over the past four weeks.

The sharp rise is likely to have been driven by those involved in the recent disorder across parts of the country.

In a new report for the Howard League for Penal Reform, five senior retired judges said the Government must reverse the trend of locking people up for longer, pointing out that custodial sentences have doubled in length in the last 50 years.

It comes as the Government’s temporary early release scheme is due to come into effect on Tuesday.

My strong view is that we should be locking up, including, sometimes for longer, those that we’re most scared of, but not necessarily everyone we’re cross with

In July, Justice Secretary Shabana Mahmood announced plans to cut the proportion of sentences inmates must serve behind bars from 50% to 40% in a bid to ease overcrowding.

Speaking to BBC Radio 4’s Today programme about sentence lengths on Saturday, Mr Chalk said: “The fact is there are some people who deserve very long sentences. We think of the Wayne Couzens, Sarah Everard case, Levi Bellfield and so on.

“But the fact is that overall sentences in Britain, in England and Wales anyway, are far, far longer than elsewhere in Europe. That is enormously expensive and the critical point is it doesn’t necessarily protect the public.

“So my strong view is that we should be locking up, including, sometimes for longer, those that we’re most scared of, but not necessarily everyone we’re cross with.”

Mr Chalk, who lost his parliamentary seat of Cheltenham to the Liberal Democrats in July’s general election, said it cost around £50,000 a year to keep a person in prison, with the capital cost of each new place around £600,000.

He said he accepted the “central premise” of what judges were saying about sentence lengths but thought the Government was right to be having a sentencing review, adding: “Let’s try to take the politics out of this and ensure that there is always the supply available to meet demand.”