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The system which sees private firms monitor criminals serving community sentences is "irredeemably flawed", the chief inspector of probation has said.

In her final annual report, Dame Glenys Stacey said people would be "safer" if supervision of offenders in England and Wales was back in public ownership.

Probation services were part-privatised in 2014, allowing firms to monitor low and medium-risk offenders.

Justice Minister Rory Stewart accepted "the current model is not working".

At the end of September, a total of 258,157 offenders were on probation in England and Wales, either preparing to leave jail having just been released, or serving community or suspended sentences.

More than 150,000 were supervised by private Community Rehabilitation Companies, with the rest - deemed high-risk offenders - managed by the National Probation Service.

But Dame Glenys said eight out of the 10 firms inspected since January last year were rated "inadequate", while public services were performing better.

Her report reveals that one firm, Sodexo, holds meetings between offenders and probation officers in restaurant-style booths in open-plan offices.

Artificial background sounds, known as "white noise", are played to prevent people from eavesdropping.

Dame Glenys, whose tenure as chief inspector ends in May, criticised the shake-up of probation carried out five years ago under then-Justice Secretary Chris Grayling.

"Above all, it has proved well-nigh impossible to reduce probation services to a set of contractual requirements," she said.

Meanwhile, the number of probation professionals is at a "critical" level, with too much reliance on unqualified or agency staff.

Last year, MPs on the Commons Justice Select Committee said the remodelling had left the probation system in "a mess".

Calling on the government to invest in probation for the next 10 years, Dame Glenys said victims, judges, the public and offenders must all have confidence in the quality of the service.

"I find it difficult to see how this can be achieved while probation remains subject to the pressures of commerce," she added.

Shadow justice secretary Richard Burgon claimed the "reckless" privatisation has left the public less safe.

"The Tories need to act on the mounting evidence, scrap their plans for new private contracts and bring probation back in house," he added.

Mr Stewart, the minister responsible for prisons and probation services, said: "We have already taken decisive action to end the current contracts early and have invested an extra £22m a year to support offenders on release.

"We are carefully considering how best to deliver an effective probation service for the future."