The trust said up to 500 jobs would have to go in the next 12 to 18 months to help tackle debts of �28.6m.

West Hertfordshire Hospitals NHS Trust said it would cut back on temporary staff to reduce the number of people in permanent posts affected.

The trust, with hospitals at St Albans, Watford, Hemel Hempstead and Northwood, recently published restructure plans.

There will inevitably be some redundancies but the board believe this will be a small number David Law

The trust's financial forecast shows that, even after delivering the current turnaround programme and making some staffing cuts over a five-year period, the hospitals would still face a deficit of �18m in 2009/10 because of changes in income and costs.

Chief executive David Law said: "Our staffing bill currently represents about 70% of our costs. Undoubtedly, we need to have fewer posts in the trust.

"We cannot manage to deliver financial balance with the 4,100 posts we currently have.

"Last year we spent over �17 million on various forms of temporary staffing.

Changes already under way

"This situation will allow the trust to reduce the number of posts it has without making large numbers of redundancies. There will inevitably be some redundancies but the board believe this will be a small number.

"I would expect to lose up to 500 posts in the next 12-18 months.

"Some of these will be part of the changes already under way - management restructuring and the medical secretary review for example.