The Queen Alexandra Hospital's redevelopment cost £255m
Nearly a hundred jobs could be axed at a Portsmouth hospital because the NHS trust which runs it needs to save £12m.
Up to 99 posts including management and clerical staff at Cosham's Queen Alexandra Hospital could go, Portsmouth Hospitals NHS Trust said.
It said it was preparing for £20bn of future cuts to be made to the NHS. To date, 62 workers have already left their jobs, according to a spokesman.
Union Unison blamed the job losses on "planning mistakes" made by managers.
Mike Wilson, from Unison, said: "We believe that there has been insufficient consultation.
"These are Unison members who provide essential services within the hospital.
"Patient services will suffer."
But the trust's chief executive, Ursula Ward, told BBC News: "The £12m deficit is the one-off cost we knew we would incur when we were moving from the Royal Haslar Hospital into our new hospital.
"It was very deliberately planned for - 70% of costs are incurred by our workforce so we need to make sure we have an affordable workforce.
"It is not a position we want to be in but we have got to prepare ourselves for the £20bn that is going to be cut out of the NHS in the next few years."
She added that "no services for patients would be comprised" and that trust had been working with "local trade unions "before it "came to its conclusion".
Services have been relocated from Haslar, St Mary's and the existing Queen Alexandra hospitals to the new facility, which has cost £255m but the final bill will be more than £1bn.
The expansion was made possible with cash from the private sector, however, it means the NHS will have to foot a £42m annual bill until 2039.
The new Queen Alexandra Hospital boasts 1,400 beds, a maternity wing, a rehabilitation centre and facilities for cancer patients.