The NHS Trust Stoke Mandeville Hospital, which is presently at the centre of a superbug scandal, was given the lowest infection-control rating in a recent set of NHS performance indicators.
The Healthcare Commission said in its report that the trust's record on preventing the spread of bugs such as Clostridium difficile was "poor" and significantly below what was expected.
The Buckingham-shire hospital, despite having a world-famous reputation for its spinal unit at Stoke Mandeville, was awarded just one star in last year's performance ratings by the Healthcare Commission.
The ratings give NHS trusts between zero and three stars, based on a series of indicators such as infection control, waiting times and death rates.
Infection control is assessed on compliance with national standards and levels of controlling bugs picked up while patients are in hospital.
The Buckinghamshire Hospitals Trust was only given a "one" rating for infection control, the lowest possible mark, and out of 177 other acute NHS trusts only 17 were given a similar score, with the majority being rated as acceptable or good.
The trust was also told it was "significantly underachieving" in terms of financial management, another reason for its one-star status.
The trust says that a key aim in its plan for 2005, is to achieve two stars in the performance ratings.
According to a spokesman the trust broke even last year and was addressing the issues raised in the performance indicators.
The rating reflects poorly on the world-famous hospital, whose incidents of C. difficile, which produces hardy spores that are resistant to some methods of cleaning, have raised fresh concerns about deteriorating cleanliness.
Those fears were fuelled when the public service union Unison warned that hospital cleaners were being told to clean as many as four wards in an hour by private companies eager to cut costs and raise profits.
A chronic shortage of cleaners and a high turnover of poorly paid staff was adding to the problem of hospital infections, says the union.
The union says the number of full-time cleaning staff has fallen by 45 per cent in the 20 years since services were "contracted out" of the NHS to private companies. In 1986, there were 67,000 full time cleaners in the health service - now there are just 36,000.