The hospitals involved were the Royal Victoria and City Hospital, both in Belfast, the Ulster in Dundonald, the Altnagelvin in Derry and the Craigavon Area Hospital.

All four wards assessed by inspectors at the Royal Victoria Hospital did not comply with guidelines. One ward at the hospital also failed a second assessment.

There were also problems highlighted in three of four wards examined at the Ulster Hospital and two of the four inspected in Belfast City Hospital.

Altnagelvin Hospital and Craigavon Area Hospital each had one ward which failed to meet guidelines.

Meanwhile, Antrim Area Hospital was the only large acute hospital in the region that did not require any follow-up inspections.

The revelations were made in the authority's 2011-2012 overview of hospital infection prevention and hygiene inspections.

The report, which was released on Tuesday, contains the findings for 45 inspections in 85 hospital wards across 30 hospital sites throughout the region.

Glenn Houston, RQIA Chief Executive, said: "It is encouraging to note that follow up inspections were not required in cancer units, brain injury units, acute psychiatric wards and community hospitals.

"We believe that a continued focus is needed, particularly in the larger acute hospitals, to make sure that all staff take on board the message of zero tolerance of healthcare associated infection."

Mr Houston explained that the inspections "focus attention on the importance of good practice in areas such as hand hygiene, use of personal protective equipment, effective cleaning practices and decontamination of equipment in fighting health care associated infections."

He added: "While good hygiene practice can help reduce infection rates, there is no room for complacency, and a clear focus on continuous improvement must be firmly embedded in all hospital wards."