The offender was among a small group of inmates given a lift from HMP Swaleside on the Isle of Sheppey, Kent, to Sittingbourne station 11 miles away as a ‘gesture of goodwill’.

An official log of the incident, seen by the Mail, says: ‘At approx 10.30hrs [the released prisoner] was being escorted by an OSG [operational support grade] in a pool car to Sittingbourne station following his release under SDS40.

‘During the journey it was alleged that [he] sexually assaulted the OSG.

‘[He] vacated the vehicle and his whereabouts are unknown at this time. The victim is understood to have had their thigh allegedly groped by the criminal.

After the vehicle stopped in the station car park he quickly left and caught a train to London. He was arrested the next day in Croydon. His release came after serving 40 per cent of a jail term for breaching a restraining order, it is understood.

National chairman of the Prison Officers’ Association, Mark Fairhurst, said: ‘I’m appalled that out of sheer goodwill a member of staff gave a released prisoner a lift and was allegedly sexually assaulted as a result. Clearly our members are at risk and this should never be allowed to happen again.’

Swaleside is a Category B medium security prison which holds about 1,100 adult male offenders. The released prisoner was immediately recalled to prison as a result of the incident, a British Transport Police spokesman said.

HMP Swaleside in Kent. The offender was among a small group of inmates given a lift from HMP Swaleside on the Isle of Sheppey, Kent, to Sittingbourne station 11 miles away as a ‘gesture of goodwill’

He has been charged with sexual assault and is due to appear at crown court next month, the spokesman added.

His release under SDS40 prompts concerns that Labour’s scheme is handing sentence ­discounts to inappropriate offenders. Tory MP Neil O’Brien said: ‘This just shows the unbelievable naivety of this scheme, which is already having horrifying consequences. People are committing serious crimes within minutes of getting out of jail.’

Other criminals freed under Labour’s early release scheme have also been sent back to jail.

One was recalled just 36 hours after being let out after failing to report to probation officers.

A prisons source said: ‘Let’s see how many have been recalled after they spend the weekend snorting coke and getting into punch-ups.’

There were sickening scenes outside jails as the first inmates were released. Criminals sauntered out of jails across the country, whooping and punching the air. Some were even sprayed with champagne by friends.