A trust is set to agree a code of practice on using hidden cameras to detect staff crime, which could be adopted across the NHS.

The NHS Executive security policy group is looking at the strategy proposed by Hammersmith Hospitals trust, which would allow spy cameras in changing rooms.

The move comes as data protection registrar Elizabeth France issued draft regulations on secret filming at work. They say hidden cameras should only be used where there is a risk of crime to 'provide evidence in appropriate cases before the court'.

Hammersmith security risk manager David Sowter said cameras would be used if there was 'a series of crimes', such as suspected theft of wallets or purses, which were serious but which the police lacked the resources to investigate.

The policy excluded 'lavatories and showers' from being filmed 'but certainly not changing rooms', he told a trust board meeting last week. 'Indeed, the first use was in the surgeons' changing room at the Hammersmith Hospital.'

Videotape from spy cameras had already been used in nurse training on the storage of controlled drugs, he added.

The policy is designed to bring procedures into line with the 1998 Data Protection Act.

Trust chief executive John Cooper promised that any plans to film secretly would 'require the consent of the staff'. He would have to authorise filming on each occasion and union stewards would be told 'the type of crime being investigated and the general area' which would be videoed.

Board members asked for further work on the policy before it could be approved.

Nursing director Georgina Dwight said: 'A number of staff will be captured on video, some in a state of undress.

'We need to be extremely clear about what we are going to do with these tapes.'

Unions warned that cameras should be a 'last resort'.

Unison deputy head of health Paul Marks cautioned: 'It has to be done very carefully, with proper safeguards.'

Trusts had a duty to 'protect staff at work' but they had to remember 'a lot of people who aren't under investigation could be being watched and filmed without their knowledge'.

Other trusts will have to bring less formal procedures into line once the Data Protection Act is implemented, which is expected to be this summer.

A spokesperson for Leeds United Teaching Hospitals trust said that cameras had been used against an abusive graffiti writer, but the trust did not have a written policy.

The Edinburgh Royal Infirmary trust also has a hidden camera available. A trust spokesperson could not confirm whether it had ever been used.