A GP service which supports homeless people has been rated as "inadequate" by inspectors.
A report by the Care Quality Commission said workers it spoke to were concerned about staffing levels at Birmingham's Health Exchange.
It said staff have a culture of high quality care, but are not supported by management.
Birmingham and Solihull Mental Health Trust said ensuring vulnerable people can access GP services is "important".
The report said the service had "a culture of high-quality sustainable care; however, this appeared not to be supported by trust management or commissioners".
However, inspectors added that the clinical team were "knowledgeable" and their concerns were "continually being raised" about limitations faced on providing an effective service.
The trust has now been given two areas where it must improve, including ensuring its care and treatment is provided in a safe way.
The report, published in October, said the exchange, based at the William Booth Centre in the city, has 1,025 registered patients.
The mental health trust which runs it said it has one salaried GP and GP support from a neighbouring practice two days a week, seven-and-a-half nursing posts, one healthcare assistant and two administrative staff.
GP hours are available Monday to Thursday and with patients directed to the local walk-in centre on Fridays.
Alan Johnson, one of the users of the service said: "I think the staff in there try with what they can but their hands are tied, they are limited to what they can do."
In a joint statement, the trust and CCG said: "Working together, and also with other partners, we have agreed a comprehensive action plan to rapidly address the concerns highlighted in the CQC report."