Sex offenders are being put up in high-street budget hotels without the knowledge of the proprietors or guests because spaces in closely monitored bail hostels are unavailable, inspectors have discovered.

The prison and probation watchdogs concluded in a damning report that not enough was being done to protect the public from sex offenders, with hundreds who had been released from jail doing no work at all to reduce the risk of reoffending.

Probation officers were not conducting sufficient safeguarding checks, including those carried out to protect children, inspectors found.

The chief inspector of probation, Dame Glenys Stacey, said: “Sexual offence convictions are increasingly common, yet despite evidence that we can reduce the risk of these individuals reoffending, little if any meaningful work is being done in prisons.

“With many probation staff unsure what to do for the best with sexual offenders under probation supervision, the public are not sufficiently protected. This makes no sense.

“There needs to be a renewed national effort to make sure all reasonable steps are taken to protect the public. Prison and probation staff need better training and support, and the opportunity to work with offenders in ways known to reduce the risk of reoffending.”

Inspectors visited five male prisons, including one that was exclusively for sex offenders and another that was for young people, examining 53 cases. A total of 120 probation cases were scrutinised in five areas.

About one-fifth of the 106,819 probation cases nationally are sex offenders – about 21,000 – and inspectors found in two-fifths of the cases they examined there had been no work focused on reducing the risk of sexual offending.

As well as two cases where offenders were sent to a budget hotel instead of approved premises, formerly known as bail hostels, there was one instance when a prisoner used another inmate’s phone account to contact his victim.

Inspectors said the jail was too slow to react and had failed to monitor mail and phone communications by the prisoners, as would be expected. There are 13,580 prisoners serving jail terms for sexual offences, nearly one-fifth of the prison population.

The joint report by Her Majesty’s Inspectorate of Probation and Her Majesty’s Inspectorate of Prisons said: “We expect prison and probation services to work with sexual offenders to reduce the risk of them reoffending and to protect the public from harm.

“In the cases we inspected, not enough work was being done, either in prison or after release, to reduce reoffending or to protect the public.

“In too many cases in prisons we found that little, if anything, was done to reduce the likelihood of reoffending, particularly in cases that were not suitable for an accredited programme (a course to help stop reoffending).”

Among the 120 probation cases looked at by inspectors, only 17 offenders had started a programme to reduce the risk of reoffending, out of 42 ordered to complete one.

The inspectors said proper safeguarding checks were not being carried out – in one-third of cases not enough was done to protect children – and more than one-third of the offenders had not received a home visit after release, which would allow staff to check who they were living with and where.

The number of prisoners serving immediate custodial sentences for sexual offences is at its highest since 2002.

Since the previous inspection of this kind in 2010, the number of registered sex offenders has risen from 34,939 in March 2010 to 58,637 in March 2018.

Nationally, there is a 25% shortfall in places for all offenders in approved premises.

The inspectors said they “saw two examples of men convicted of sexual offences being released to budget hotels or other temporary accommodation. We found it hard to see how such accommodation could be defensible in terms of protecting the public. Other hotel residents are likely to be transient, and close monitoring of the offender problematic.”

In probation, there were 42 cases where the offender should have faced enforcement action for failing to attend appointments, breaching licence conditions or committing another offence.

But in nearly half the cases, no action was taken by the responsible officer.

The watchdogs made a series of recommendations, calling for “urgent and much-needed progress in the management and supervision of sexual offenders”.

The chief inspector of prisons, Peter Clarke, said: “We found too many cases in prisons where little, if anything, was done to reduce the likelihood of reoffending. This is serving neither the public interest nor that of those prisoners who need help to change their behaviour before being released back into the community.”

The prisons minister, Rory Stewart, said the government “will work very hard” to ensure convicted sex offenders are no longer housed in hotels upon their release from prison.

He told the House of Commons this had happened in a “very small number of cases” and estimated of the roughly 10,000 people released each year, “54, 55, sometimes 56 of them will end up being in some form of emergency accommodation”, and of those, “something like half a dozen would end up in this form of hotel accommodation”.

Stewart added: “Before they’re put in that type of accommodation, police and probation services will have conducted a very detailed risk assessment and would have ensured that the individual put in that type of accommodation is not an individual who posed a risk of a contact offence to a stranger.”