A formal warning was issued over cleanliness and hygiene issues at the A&E at St Mary's Hospital.
Three hospitals in west London have been told by inspectors they "require improvement".
The Care Quality Commission criticised some of the care and conditions at Charing Cross, Hammersmith and St Mary's Hospitals.
Inspectors found at least one A&E was found to have broken equipment and was dirty.
Imperial Healthcare NHS Trust said it was not good enough and that it would redouble its efforts on cleanliness.
Inspectors found curtains of bays had brown stains on them and these had last been changed in February 2014.
Some equipment was held together by tape - such as a drip stand and a patient monitor - while an anaesthetic machine had been out of order for six days.
A portable X-ray machine labelled "clinically clean" was found thick with dust.
Inspectors found there were not enough nurses
Inspectors also saw unbagged, soiled linen on the floor next to two linen bags that were full, one of which was outside the treatment room.
The inspection, which was carried out in September, also found:
- Nurse staffing levels were not sufficient in some areas, especially in medical wards, and there was a high reliance on bank and agency staff
- The surgical department had a significant backlog of patients waiting for elective surgery. Referral times in some specialties had breached national targets on an ongoing basis
- Charing Cross Hospital was rated as "requires improvement" overall; its A&E and end of life care were rated good
- Its medical care, surgery and critical care required improvement while its outpatient service was "inadequate"
- Hammersmith Hospital was also rated as requiring improvement overall by inspectors
- Its outpatient services were inadequate, while all other core services at the hospital were rated as requiring improvement
- St Mary's Hospital required improvement overall while A&E and outpatient services were rated inadequate. Medical care and surgery were rated as requiring improvement
Following the inspection, CQC issued the trust with a formal warning over cleanliness and hygiene issues in A&E at St Mary's Hospital.
Inspectors have since returned and found the required improvements had been made.
The hospital's A&E department has been under pressure recently as it takes on more patients following the closure of Hammersmith Hospital's A&E department in September.
CQC's chief inspector of hospitals, Professor Sir Mike Richards, said although staff delivered compassionate care, there was too much variation in the quality of services.
"People are entitled to receive treatment and care in services which are consistently safe, effective, caring and responsive to their needs," he added.
Dr Tracey Batten, the chief executive of the trust said: "There's no doubt that what was found by the CQC was not good enough in the A&E department and we really need to redouble our efforts to ensure the standards of cleanliness and hygiene are our number one priority down there."
16 December 2014 Last updated at 17:56