Healthcare Improvement Scotland (HIS) has made 21 recommendations to NHS Lanarkshire which it says are necessary to deliver safe and effective patient care at Monklands, Hairmyres and Wishaw hospitals.
Scottish Health Secretary Alex Neil said he expects the improvements to be delivered urgently.
Mr Neil ordered the rapid review in August after data showed that each of the hospitals had had a mortality ratio significantly higher than the Scottish average at some point in the previous 18 months.
Updated analysis later showed Hairmyres and Wishaw hospitals fell within the accepted range, but data from Monklands remained significantly higher than average.
The review states a higher than predicated mortality rate cannot be used to make judgements about the quality and safety of health services, or be used to quantify the number of avoidable deaths, but can be used as a "smoke alarm" to alert a health board to potential problems.
It found it was not possible to draw definitive conclusions about the causes of the higher mortality rates, but late submission of records, the accuracy of diagnosis recorded in clinical records and quality of care could be factors.
The review team heard the experiences of 300 patients and carers, listened to over 200 members of staff, visited more than 40 clinical areas and reviewed 152 records of patients.
Robbie Pearson, director of Scrutiny and Assurance at Healthcare Improvement Scotland and chair of the review team, said: "Although the review team found a service where clinicians and managers are working hard to do the right thing, sometimes in a difficult environment, the team concluded that a broad range of improvements are necessary for NHS Lanarkshire to continue its commitment to delivering safe and effective patient care.
"This includes the need for stronger focus and leadership in implementing robust patient safety interventions and in the redesign of services."
Mr Neil said an expert team would be appointed to help NHS Lanarkshire implement the recommendations.
He said: "This report highlights the importance of the Scottish Patient Safety Programme. It also shows that at times the standards of care have fallen short of the Scottish Government's expectations for patients.
"Today I am announcing that we are providing a Governance and Improvement Support Team to work with NHS Lanarkshire to help them deliver the rapid and sustained improvements which are needed.
"I expect those improvements to be made urgently, and I have asked to be updated regularly. I have also asked for a formal review of progress against the recommendations by the end of March.
"We should not lose sight of the commitment and dedication of staff across NHS Lanarkshire and the whole of our health service."
NHS Lanarkshire chief executive Ian Ross said: "Delivering high quality care is our priority and we recognise that it is right and proper that the health service is subject to the highest level of scrutiny to ensure this is being achieved. We regret any occasion where patient care has fallen short of the high standards we strive for.
"Having just received the report we need to go through the findings in detail with our clinical leaders, with Healthcare Improvement Scotland and with other stakeholders. We accept the recommendations and recognise many of them as areas where we are already making improvements."
Dr Neil Dewhurst, president of the Royal College of Physicians of Edinburgh (RCPE), said: "The findings of this review make depressing but not surprising reading.
"They are an indication of systems under severe pressure and prevalent in unscheduled care. Clinicians across Scotland will recognise the challenges facing colleagues in Lanarkshire.
"Doctors and nurses work under severe pressure with rising numbers of patients treated by a workforce with high locum levels and local recruitment difficulties. Insufficient senior review, particularly out of hours, an over-reliance on junior doctors and poorly resourced quality improvement systems contributed to a downward spiral of quality.
"Quite simply, clinical teams in Lanarkshire were unable to provide the quality of care that patients have a right to expect and which are enshrined in national quality standards. It is not surprising that a statistically significant increase in mortality rates in patients were evident."
He added: "The NHS is one of our most important assets. We have a collective responsibility to ensure that it is sustainable, properly supported and that we provide the standards of care that patients deserve and doctors and nurses want to provide."