Tony Spotswood calculates that £8million could be found through joint procurement and £12million through streamlining back office and management support in the merged trust.

Other savings will be made through only needing one chief executive, one finance director and one board of directors.

Three months of public consultation are due to start on Wednesday, but only over the way the combined trust would be governed and to invite suggestions for what it should be called. The individual hospitals will retain their current names.

The NHS Competition and Co-operation Panel and the Office of Fair Trading will be looking closely at whether the benefits to patients of merger are likely to outweigh any benefits of having two hospitals in competition.

“What most patients want is good quality clinical services, which is what this is about. The real issue is about sustainability,” said Mr Spotswood.

Only after a merger has taken place can clinicians look at the way their teams are run and whether there is scope for reconfiguring services. Any major changes, such as concentrating a service on one site, will have to go out for further public consultation.