Barnet and Chase Farm Hospitals NHS Trust is discussing plans with the Metropolitan Police to train staff to be special constables, who will patrol the corridors and wards armed with the powers of a normal police officer.

The news comes as statistics obtained under the Freedom of Information Act revealed that 205 allegations of theft had been recorded from patients, staff and visitors at Barnet and Chase Farm hospitals in the past five years.

The figures emerged after a dead woman's diamond ring was reported stolen at Barnet Hospital. Between the death of Joan Marguerite Keil, 87, of Waterfall Road, New Southgate, on January 12, and the time her body was picked up by undertakers, her yellow gold diamond solitaire, a family heirloom estimated at around £3,000, went missing and has not been found since.

A spokeswoman said the trust was talking to the Met about introducing Hospital Watch, a scheme which sees hospital staff trained by police and given the power to arrest and stop and search suspects.

They will be released from duties to receive training to become special constables, and will then patrol the hospital, once a fortnight, alongside experienced officers.

The trust also wants to step up the number of patrols on hospital grounds.

Security will also be improved at the hospitals, in Wellhouse Lane, Barnet, and The Ridgeway, Enfield, with better lighting and extending CCTV coverage.

Mrs Keil's daughter-in-law, Joan Keil, said the family had asked for her jewellery to be recorded by staff but this was not done because they were overstretched. She welcomed the news of the proposed measures, saying: "It needed to be done ages ago. If we had been aware that the hospital had a problem with theft, we would have made such a stink about getting the possessions protected. It would have saved us an awful lot of distress."

A trust spokeswoman said: "The trust recognises that it has a responsibility to provide a safe and secure environment for patients, visitors and staff. However this has to be balanced with the fact that the hospital is a public place which is occupied and visited by thousands of people every day."

She added that the Keils' situation underlines the importance of documenting personal belongings, and said it was regrettable that this did not happen in their case.

"As a consequence of this incident we will be reinforcing to our staff the importance of documenting patients' personal effects," she continued.

"We are also in the final stages of developing a patients' property policy and there will be a staff awareness campaign when this is launched."