A team of 14 hospital managers and clinical staff spent thousands of pounds on a fact-finding mission to America -- to find out how to tackle mounting debts.
The visit, which is thought to have cost about £5,000, has been criticised by unions and politicians.
Critics have questioned why the team from the Oxford Radcliffe Hospitals Trust travelled to Boston, in Massachusetts, at the end of April -- around the time their chief executive Mike Williams was holding a special meeting to discuss about how to make £12m of cuts.
The trust recently cleared a £20m deficit by selling the Radcliffe Infirmary, but has warned it could experience a similar overspend within the next 12 months unless strict savings are made.
Managers said they had returned to the UK with a list of ideas which could be implemented to improve the trust, which is responsible for Oxford's John Radcliffe, Churchill and Radcliffe Infirmary, and The Horton, Banbury.
The fact-finding party, led by ORH medical director Dr James Morris, visited Massachusetts General Hospital, Beth Israel Deaconess Medical Centre, and New England Medical Centre, over three days.
Banbury MP Tony Baldry, who has called a public meeting tonight to discuss concerns The Horton could be downgraded to help cut costs, criticised the move.
The trust has denied any plans to downgrade or close The Horton, saying it will remain a "fully functioning general hospital". But Mr Baldry said many people remained unconvinced.
He said: "The ORH's finances are in chaos and it strikes me as slightly bizarre to find out that staff are flying out to Boston. You could get a financial or medical director at any UK hospital to come and give you advice instead.
"I think they need an external investigation to find out why their finances are in such a bad way. Someone should be investigating the debt at home."
Mark Ladbrooke, chairman of the Oxfordshire health branch of the Unison union, said: "It seems strange they need to take so many people on the trip. "If they have information that Boston has a radical way of doing things, then that's fine, and nice to see they're interested, but it would have to be justifiable to send one person, let alone such a big group.
"I have no problem with them learning from international experience. Cuba's health service, for instance, has some of the lowest waiting times in the world -- but maybe the shopping is not so good."
Dr Morris, who used to work in America, defended the trip.
He said: "Beth Israel Deaconess Medical Centre had a $60m deficit about three years ago. We were interested to see how they had approached the deficit by making their services more efficient.
"We used our study leave for the trip, so there was no additional cost to the trust, and it all came from the study leave budget. It would've cost us no more money than we would have spent anyway. It just won't be available later in the year."
He said Massachsetts General was regarded as one of the best hospitals in the world, and the ORH team visited to learn how to reduce cancelled operations and use theatres more productively.
Anaesthetist Dr Mike Sinclair, ORH clinical chairman of surgery, said: "There's no big trust in the UK that does what we do, and we went to Boston mainly to get information about surgical input.
"Everyone put a great deal of effort into helping us and it was very enlightening. We had to go there -- it wasn't something we could do over the phone or via tele-conferencing."
The public meeting, in Banbury Town Hall at 5.30pm, will be chaired by Banbury's mayor Rosemarie Higham and attended by county, district, and town councillors, as well as local GPs and hospital staff.
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