Scotland's prison watchdog has warned issues with the water supply at the country's largest jail are a symptom of its ageing estate.

Some inmates were left unable to flush toilets in their cells at HMP Barlinnie in Glasgow while others have had "intermittent" access to hot water for seven days.

Sara Snell, His Majesty's Chief Inspector of Prisons, said overcrowding at the jail had exacerbated existing problems with "inadequate" infrastructure.

The Scottish Prison Service (SPS) said work to fix the issues was ongoing, but was causing "disruption" in a small number of areas.

The Scottish government has been contacted for comment.

A total of 1,415 men were being held at the prison when an inspection took place on Wednesday – almost 400 more than the designed capacity of 1,021.

About a quarter of those were being held on remand, Snell said.

BBC Scotland had been contacted by several friends and family members of inmates who said they were concerned about their welfare.

Some were left without any running water in their cells and had no access to bottled water when issues began last Thursday.

Snell acknowledged the SPS had "implemented contingency measures" including handing out bottled water and using mobile water tanks for toilets and showers.

But she said the incident was further proof that a replacement facility was needed.

"This incident reinforces our longstanding concerns about the inadequacy of the ageing infrastructure at HMP Barlinnie, and the risks associated with continued heavy reliance on a deteriorating estate," she said.

"As well as our concern for the conditions and treatment prisoners experience when in prison, this incident also highlights the wider vulnerability of the prison estate in the context of ongoing overcrowding."

HMP Glasgow, a replacement for the 143-year-old Barlinnie, is expected to open in 2028 at a cost of almost £1bn.

It was originally scheduled to open in 2025 and had been estimated in 2022 to cost about £400m.

Snell said contingency arrangements should remain in place and called for a reduction in the number of prisoners being held.

Water supplies have had to be temporarily isolated while repair works were carried out.

Some inmates have been moved around the estate in order to access hot water for showers.

An SPS spokesperson said: "Throughout the last week, our focus has been on maintaining essential services and ensuring access to drinking water, sanitation, showers, food provision and healthcare.

"Necessary work remains ongoing and is continuing to cause some disruption in a small number of areas."