Unions and contractors have warned that the private finance initiative pilots - working on a model for transferring NHS staff to private companies - still face huge problems in agreeing contractual arrangements, despite Unison's acceptance that the pilots can proceed.

Facilities staff working in the PFI sites will first have to resign from the NHS and be reemployed by the trusts for the retention of employment model to work. And Unison has made clear it would pull out if it was not satisfied with the final contractual arrangements.

Staff would resign and transfer to the contractor as part of the secondment model. They would then be re-employed by the trust on the new contract, with their NHS pay, conditions and pension rights guaranteed. The mechanism was worked out to allow the government to get round the TUPE regulations.

Under the proposals accepted by Unison, an estimated 85 per cent of NHS facilities staff would remain NHS employees. The other 15 per cent - supervisors and managers - would transfer to the private companies. The agreement now includes security staff, as well as porters, cooks, cleaners and laundry staff.

Unison head of health Bob Abberley said: 'It has always been accepted that it would be evaluated and either side could withdraw.

Health minister John Hutton set a target of the end of the year. I think we are looking at a three-month agreement. The issue is whether the agreement we have reached can be expressed in a contract, and, from the government's point of view, if we have a contract, if value for money can be achieved.'

Norman Rose, director general of the Business Services Association, which represents private facilities companies, told HSJ it would not be acceptable for any other projects to use the model yet, because it had not been properly tested. 'This is a new model that is totally untried. It is going to take at least 12-18 months after staff second to the private sector before we know if this will be a workable model. My concern is that if this becomes the norm, we could have a lot of projects pushed down this line. We know there are eight projects in the wings including soft services.

'Three months is simply going to sign the deal. It is not going to say it is going to work.'

HSJ sources have said there will be ongoing problems with a twotier workforce, with some staff employed by the NHS and others by the private companies, and are also concerned that the deal has only been agreed with one union.

Even if the pilot contracts proceed successfully, it will be up to nine months before work could actually start on new buildings.

Unison's agreement to the contractual negotiations came a day after it gave evidence to the House of Common's public administration committee's inquiry into public service reform. It told the committee that it took huge amounts of resources to get schemes up and running. Unison national officer Margie Jaffe said: 'We have had the chief executives of NHS trusts say to us that other reforms have had to go on hold while they and senior managers have had to work on PFI schemes.'