Around 1,750 convicts were freed this month as part of a government scheme that made some prisoners eligible for release after serving 40% of their sentences behind bars, down from 50%. Thousands more are expected to be let out.

A justice ministry spokesman said in a statement, confirming a report by the Daily Mirror newspaper on Wednesday, that a very small number of offenders, charged incorrectly and sentenced under outdated legislation, had been released wrongly.

“The convictions remain valid with offenders monitored since their release and they will soon be back behind bars,” the spokesperson said.

“Public safety is our first priority.”

A total of 37 prisoners in prison for breaching restraining orders were incorrectly released but a majority are already back in prison. Five offenders have not yet been returned to custody.

The ministry said the charges against the 37 were brought and progressed through the court under old legislation incorrectly, meaning the sentences were not identified as being ineligible for the early release scheme.

The UK has western Europe’s highest rate of incarceration, and faces a crisis as tougher sentencing laws and long delays in the justice system have fuelled a growing prison population.

After taking office in July, the Labour government said prisons could be full within weeks and early release was needed.

Prisoners serving sentences for serious violent offences of four years or more were excluded from the scheme.