A health union and an MP have warned that services could be damaged if savings being considered by Gwent Healthcare NHS Trust are brought in.
The Trust runs 23 hospitals across the authority area
Monmouth MP and AM David Davies has seen a copy of an efficiency plan to help tackle the trust's £43m deficit.
He fears job losses, rising car parking charges and a poorer patient service.
The trust needs to save £20m over two years and said it was looking at new ways of delivering services which could result in improvements for patients.
The trust runs 23 hospitals across the authority area and employs more than 13,000 people.
It is considering a number of options to making the savings.
The proposals revealed by Mr Davies include money-making ideas like increasing car parking charges and allowing mobile phone companies to install masts on hospital buildings.
He said: "They're looking at what they call utilisation of ward space, I think that translates as closures.
"They're talking about selling space to phone companies to put up masts on the roof.
"They're also talking about increasing the car parking charges which are already very high and are affecting both staff and visitors."
The proposals could also mean up to 80 medical secretary jobs could be lost, with the work being exported abroad.
The health union Unison condemned the plans.
David Galligan said: "If you close hospitals, close beds, there's only one loser and that the patients.
"We've obviously got a vested interest in looking after our members' interests but we're all service users potentially.
"We could need those beds, those facilities, and they won't be there, and once they're gone, they won't come back.
"Hospitals close, hospitals get mothballed. They don't re-open and that's the frightening future of healthcare in Gwent."
The trust said it had not made any decisions, but was looking at "new ways of delivering services" which could result in "improvements in quality" for patients.
It said: "Our trust board agreed a strategic change and efficiency plan on 23 September 2006 aiming to deliver savings of £20m over two years.
"This amounts to a significant contribution to the projected financial shortfall that faces the whole health community".