Probation officers have been given as little as a week’s notice to prepare for serious offenders to be freed in England and Wales under the government’s early-release scheme, the Guardian has been told. About 2,000 prisoners are expected to be let out on Tuesday 10 September amid warnings of a coming spike in crime. But members of the probation officers’ union Napo were only informed on 3 September that this would include some serious offenders being released into their supervision. Officers are usually given more than three months to prepare services to help monitor and rehabilitate a serious offender. The development comes as the prison population reached a record high on Friday. The justice secretary, Shabana Mahmood, said in July that the SDS40 scheme – under which offenders with standard determinate sentences will be released after they have served 40% of their term – would be introduced in September to give the Probation Service time to prepare. Tania Bassett, a national official at Napo, said: “Our members from across the UK have not been given eight weeks to prepare for the high risk of harm of some dangerous offenders. “We have received reports of late information about releases from the north-east, Reading and other areas. “In some cases, our members were told on Tuesday – a week before the early release date – that serious offenders would be released in their area.” She said the number of recalls of offenders was expected to rise because of the increased workload on officers. “If prisoners are released so late that our members are given a few days to prepare for people who may be serious offenders, then, inevitably, recalls are likely to go up.” While the majority of people being released under the scheme will be lower-level offenders, there have previously been serious incidents after prisoners were released on licence, including Jordan McSweeney, who murdered two days after he had been recalled to prison. The union said some members have said the early release scheme has left them feeling further exposed to persecution if their clients commit a serious offence. One officer told the union: “We don’t feel protected. It feels like the service doesn’t care about us.” The probation watchdog has told the Guardian that “a small proportion” of the 2,000 offenders due to be freed could be expected to go on to commit serious crimes. Martin Jones, the chief inspector of probation in England and Wales, said that late information about who was being released would place “huge additional pressures” on probation staff. “The eternal optimist says that the scheme will go well. But the realist in me says that some of those released will go on to reoffend, and a small proportion of those will be serious offences,” he said. About 300 offenders on probation commit serious further offences every year, which relate to specific violent or sexual offences that make them a particular risk to the public. Under the SDS40 scheme, an estimated 2,000 prisoners serving sentences of less than five years will be released on 10 September, followed by a further 1,700, who are serving sentences of more than five years, on 22 October. The scheme was announced by Mahmood days after the general election amid warnings that the criminal justice system was on the brink of collapse. Official figures showed there were 88,521 people in prison on Friday, 171 more than the previous record set at the end of last week. 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. “That is why the new lord chancellor announced in July that she was scrapping the previous government’s early release scheme, replacing it with a system which gives probation staff more time to prepare for a prisoner’s release and a live database for affected cases that staff can check in real time.”