The former Conservative justice secretary Alex Chalk has said judges should stop locking up “everyone we’re cross with” and instead focus on keeping the criminals “we’re most scared of” behind bars.

Chalk’s remarks came after official figures published on Friday showed that the prison population had reached a record high, with 88,521 people behind bars in England and Wales.

Next week, about 1,500 people are due to be released from prison early under an emergency measure to free up space.

Chalk told BBC Radio4’s Today programme on Saturday: “There are some people who deserve very long sentences. We think of the Wayne Couzens, [the] 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.”

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

He was responding to a report by the five most senior retired judges in England and Wales, which points out that custodial sentences have approximately doubled over the past 50 years and calls on the government to reverse the trend of “sentencing inflation”.

The paper, by the Howard League for Penal Reform, highlights the fact that the number of people in prison was about 40,000 in 1991 – less than half the population of prisoners today.

However, the paper indicated that the main driver of sentence inflation was the introduction of statutory minimum terms for murder in 2003.

Chalk said he accepted the “central premise” of what judges were saying about sentence lengths, but thought the government was right to conduct 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.”

About 2,000 prisoners are expected to be let out under the government’s early release scheme, which comes into force on Tuesday, with prisoners serving standard determinate sentences allowed to leave after completing 40% of their term.

Members of the probation officers’ union, Napo, say they have been given a week to prepare the service to help monitor and rehabilitate some of the serious offenders being released into their supervision – preparation which normally takes more than three months.

After an investigation by Channel 4 News revealed that prisoners who had committed serious offences were being allowed to leave prison early, the Ministry of Justice confirmed that prisoners who have completed a sentence for a serious crime, and are now serving a consecutive sentence for a less serious one, would be allowed to leave prison after completing 40% of the term for the less serious crime.

At the time, a Ministry of Justice spokesperson said: “The new government inherited a justice system in crisis, with prisons on the point of collapse. It has been forced to introduce an early release programme to stop a crisis that would have overwhelmed the criminal justice system, meaning we would no longer be able to lock up dangerous criminals and protect the public.”