Barlinnie bosses have warned it faces a “catastrophic failure” as a new prison has been delayed.

The governor of Scotland’s largest prison has raised concerns as the completion date for the 140-year-old jail’s replacement has been pushed back.

HMP Barlinnie was ruled to no longer be fit for purpose in 2020, with a new jail initially set to open in 2025 to replace it – but the deadline has now been pushed back to 2027.

It comes as the Glasgow jail is running at 140% capacity with just under 1,400 prisoners when it was designed for 987, according to governor Michael Stoney.

The state-of-the-art replacement is expected to include a reduction in the size of housing blocks from 30 to 20, and will see football pitches and en-suite cells introduced.

In April, First Minister Humza Yousaf said he would investigate an estimated £300 million overspend on the replacement HMP Glasgow.

But Mr Stoney said the current prison cannot handle more delays.

He told the BBC: “This prison can’t last that much longer. The infrastructure fails constantly.

“At some point it may be a catastrophic failure, by then it’s too late. We know that day is coming.

“A lot of my time is just trying to keep the prison functional. If dates like building and completion stretch further, then the risk gets greater year on year.”

An inspection in 2020 found overcrowding at the notorious prison could be in breach of UN human rights agreements.

Mr Stoney also highlighted issues with the prison’s ability to prevent strong drugs being smuggled in, keeping enemy prisoners separate, and staff assaults.

The governor said the new prison could lead to a 20% reduction in re-offending due to increased rehabilitation services.

He said: “I have made bold inferences that we would reduce reoffending by the people that pass through our doors by about 20%.

“That’s because, if we are confident in our capacity and the professionalism of our staff and the care and compassion they have, they will make a huge difference if given the time.

“We have to be bold about it – we are getting a big investment and we have to be bold by saying we’ll give you a big return.”