Unison members have voted for a week-long strike in a further escalation of their dispute over a private finance initiative deal in Dudley.
The 600 mainly ancillary workers at Dudley Group of Hospitals trust have also called on health secretary Alan Milburn to intervene.
Staff struck for four days last week against their transfer to private contractors under the terms of the£80m scheme. The strike followed a 48-hour walk-out earlier this month.
Unison national officer Steven Weeks said action was being planned 'in a phased way' because the union wanted 'to give an opportunity for the Department of Health and the government to respond'.
The trust says 'the door is still open for talks' but the 'desperately needed' PFI deal cannot be renegotiated.
Ninety-eight operations were postponed during the 48-hour walk-out.
The trust said last week's strike was 'less disruptive'.
A spokeswoman said the trust had switched to airline-style meals and disposable crockery and cutlery to help keep services going.
'People have come in from holiday and we have had directors take on cleaning and driving jobs in addition to their normal workload.'
NHS head of private finance and capital Peter Coates wrote to the trust last month saying it would be 'impossible to sanction' re-tendering the project.
The government changed the rules on PFI last June so staff could be excluded from schemes. But Mr Coates told the trust that the new rules do not apply to deals that went out to formal tender before then.
Mr Weeks told HSJ : 'The trust is claiming it has gone as far as it is allowed to under the current rules, so we are asking the NHS Executive to review that.'
The trust and Unison both said attitudes were 'hardening' as the dispute progressed. At a strikers'meeting this week, a sizeable minority called for indefinite action.
Other third-wave PFI schemes are taking a mixed approach to staff transfers.
Jackie Hadwen, single-site project manager at Blackburn, Hyndburn and Ribble Valley Healthcare trust - which excluded ancillary services from its£70m PFI tender notice - said the decision had been taken after a benchmarking excercise.
'The trust board wanted to be as fair as it possibly could to staff. That was the reason for looking at it as they did - but it was a value-for-money assessment.'
Northumbria Healthcare trust has reached 'preferred bidder' stage with support service staff excluded from a£28m project to replace World War Two Nissen huts with a new Hexham hospital after a similar assessment, finance director Ian Renwick said.
The trust felt 'there wasn't a clear financial benefit to transferring the services' out of the NHS.
But Southern Derbyshire Acute trust PFI project manager Steve Maleham said the trust 'envisaged' maintenace, cleaning, catering and portering being included in its£140m scheme.
It wanted to 'keep its options open' to include other non-clinical services such as IM&T and sterilisation services as well, he said.