Improvements must continue into surgery services at Poole Hospitals NHS Foundation Trust, according to England's Chief Inspector of Hospitals
The finding come following its latest inspection by the Care Quality Commission (CQC).
The group undertook an unannounced inspection in June 2018 after it received information of concern from whistle-blowers.
It found that the hospital needed to take action on the following concerns;
Safety and quality of patients' care in surgery. At times care and treatment were not always provided in a way that reduced risks to patients.
Staff did not always carry out their work in a way that prevented and controlled infection.
Policies and procedures were not always followed in relation to the management of medicines.
Arrangements currently in place, to assess, monitor and improve the quality of services provided to people were not operated effectively.
Adequate processes were not in place to ensure the premises were properly maintained.
Systems to ensure staff received appropriate support, professional development, supervision and appraisal were not operated effectively.
"The Warning Notice sends out a clear message to the trust where it must take action to improve. The chief executive has assured us that board are fully sighted on the issues we have raised.
Inspectors also found that although safety incidents were reported, investigations were not always concluded quickly enough, or communicated effectively to allow the improvements to be made.
Staff working in theatres did not always feel that safety was prioritised in relation to compliance with the World Health Organisation safer surgery checklist. Staff knew how to raise concerns, but some told inspectors they did not always feel comfortable to do so.
The service did not always act promptly on feedback.
In the national staff survey, the surgical care group scored substantially lower than the trust overall in six areas, including harassment and bullying.
The Trust has responded to the CQC report.
"Our theatres are always busy, but at the time of the CQC inspection, we were experiencing significant staff shortages and were dealing with an unprecedented number of trauma admissions. As a consequence, at that time, we failed to meet our usual high standards. The CQC's report highlighted a number of areas that needed attention, but the Trust was aware of these and had already started taking steps to address them.