Standards at Dartmoor, one of Britain's oldest and most notorious jails, have deteriorated since it was last inspected, a report said on Wednesday.

Named after the bleak, windswept moor where it stands in Devon, Dartmoor has gained a reputation as one of the the harshest jails since it was built in 1809 to house French captives during the Napoleonic Wars.

Two years after her last inspection, Chief Inspector of Prisons Anne Owers said she was concerned by the prison's management and the use of force, which had doubled since 2006.

In her latest report, issued after an inspection in February, she said one particularly serious incident had not been investigated internally, and criticised "institutional disrespect", poorly furnished cells and dirty areas.

"It is always disappointing to report on a prison which has not been able to maintain promising progress," Owers said in a statement.

"Dartmoor has significantly slipped back from the prison we inspected in 2006. It will require renewed and much more robust management to reverse this trend, to support and encourage committed staff."

The Director General of the National Offender Management Service, Phil Wheatley, attributed the prison's problems to governor Serena Watts not being at the prison enough.

Prison sources said Watts had undergone major surgery, but was back to full health.

"In the months running up to this inspection, the governor had spent a significant but unavoidable amount of time out of the prison, and this undoubtedly contributed to the prison slipping back in its transformation since 2001," said Wheatley.

"I'm confident that the governor of Dartmoor and her current senior management team will continue their hard work to ensure that ground recently lost is regained."

In 2002, Owers described Dartmoor as "the prison that time forgot" with some areas little changed since it was built.

Conditions were so bad in 2002 that the report of that year compared them to the controversial U.S. camp at Guantanamo Bay, Cuba, where Taliban and al Qaeda fighters from Afghanistan are being held in wire mesh pens.