Bromley Hospitals trust has been rapped for breaching the hygiene code after a Healthcare Commission spot check.
Inspectors found "a thick layer of dust" on curtain rails around beds and bloodstains on a bed and wall during the unannounced inspection at Princess Royal University Hospital last month.
The inspectors also raised concerns about effective decontamination of equipment after discovering that commodes marked clean and ready for use were soiled underneath.
The trust was issued with an improvement notice after the visit, which was part of an extensive programme of inspections relating to hospital infections.
Trust chief executive Ian Wilson told HSJ he was disappointed with the findings but said that they did not alter the fact that real progress had been made on cleanliness and infection rates.
"Our MRSA and C difficile rates are up there with the strong performers in London," he commented.
"We haven't always been in that situation and that's through people working very hard on those issues. This shouldn't be used to write off the really good work that has been done."
The trust has already fulfilled an urgent requirement to introduce a "robust" system to keep track of surgical instruments sterilised in desktop machines, said Mr Wilson.
It has until the end of the month to address cleanliness issues and has met with private finance initiative partners UnitedHealth and ISS Mediclean to draw up an action plan.
"There has been a very strong message out in the trust that we have to be clear about each person's role in the cleaning regime and for managers to check everyone's doing what they're meant to have done," said Mr Wilson.
"That has been useful, particularly in areas where the cleaning staff and healthcare assistants both have duties with regard to cleaning some equipment."
He concluded: "I am absolutely confident that by the time the commission comes back we will be performing at the level of the best performers on cleanliness."