An independent inspection of maternity units run by Great Western Hospitals in Bath and Swindon has found there were not enough midwives.
As a result the Care Quality Commission (CQC) has ordered the GWH NHS Foundation Trust to take action to improve staffing levels.
The Princess Anne Wing, at the Royal United Hospital but run by the GWH Trust, was also ordered to take action on cleanliness and infection control after the commission found essential standards were not being met.
The CQC also visited Trowbridge Community Hospital’s birthing centre and found it met the essential standards for staffing, cleanliness, infection control and care and welfare of patients.
The maternity services at all three hospitals are run by Great Western Hospitals NHS Foundation Trust, which said it was developing an action plan in response to the CQC findings.
The CQC inspected all the units in December and published its findings today.
At the Princess Anne Wing, the commission said some GWH Trust staff felt there were not enough staff on duty as demand for hospital births increased.
The GWH Trust said its ratio of midwives to births at the Princess Anne Wing was one midwife to 38 births but the national recommended ratio is one midwife to 28 births.
On cleanliness the CQC said: “We were told patients and their partners found the hospital clean and well organised. During our inspection we found the arrangements for cleaning did not provide staff with a clear definition of specific roles and responsibilities.
"The environment was not maintained in some areas to facilitate prevention and control of infections.”
The Bath maternity unit delivered 4,003 babies in 2011/12 - an increase of just under 600 births since 2008/9.
At GWH, Swindon, the commission was told that the ratio of midwives was one to 44 births.
The GWH Trust said it was short of almost six full time staff in the acute maternity unit in Swindon but was exceeding staffing levels on the midwife-led White Horse Birthing Centre in the hospital.
The GWH Trust delivered 3,700 babies in the acute maternity unit and 877 in the White Horse Birthing Centre in 2011/12, an increase of just under 550 births since 2008/9.
Both GWH and the Princess Anne Wing in Bath met the other standard inspected by the CQC of respecting and involving patients.
At Trowbridge Birthing Centre the CQC was told by a member of staff that patients and staff valued the continuity of care they were able to give people. The centre deals with low risk births.
Hilary Walker, chief nurse at the GWH Trust, said: “Improving staffing has been identified as a priority at the Great Western Hospital and at the Princess Anne Wing, as it is for many other maternity services across the country.
"We have already started planning to increase the number of qualified, skilled and experienced midwives supporting these services.”
She said the GWH Trust had just secured £400,000 from the Department of Health to refurbish the Princess Anne Wing which would make cleaning and infection control measures much easier and more effective.
She said: “We are pleased that, although there are further improvements to be made, feedback from women remains positive across all of our maternity services with particular praise given to the attitude of our staff.”