Great Western Hospital bosses have cited frustration and disappointment over ongoing "serious issues" with catering and cleaning firm Carillion.
Board papers describe a "lack of confidence" in Carillion, calling on it to "resolve these issues once and for all" with a detailed action plan.
Carillion was given a one-star food rating in April and has been in dispute with its staff since 2011.
The firm accepts its quality fell but says it is improving standards.
A spokesman for Carillion said: "We are confident that there is not a risk to the safety of patients.
"We continue to work with the Trust to make further improvements to services for patients, visitors to the hospital and the Trust staff."
In April, the Food Standards Agency gave Carillion low marks for the way it stored food and recorded temperatures at the hospital.
Other issues included out-of-date and uncovered food stored in freezers.
An improvement notice was served and this was lifted in June, although the one-star rating remains.
The report, which hospital directors are due to discuss later, also touches on staffing problems.
'Blunt and unambiguous'
Director of strategy at the hospital, Kevin McNamara, said: "We want them to double their efforts.
"We're absolutely unapologetic for being as blunt and unambiguous as we are in terms of getting them to resolve these problems - ultimately this is about patient care."
Some 50 of its staff have lodged employment tribunal claims against Carillion.
The trade union has also been in dispute with the firm over holiday entitlement, working practices and other concerns for the past three years.
This issue was described in the report as a "clear distraction from the service we require and pay for".
Carillion is not directly employed by the hospital trust - instead it is employed by the building owner Semperian - under a Private Finance Initiative (PFI) contract.