The Care Quality Commission (CQC) has published its first national assessment of health and adult social care services, warning there is poor care being provided by some.
Hospitals and trusts assessed and rated as good or outstanding comprise only 38% of those assessed by the CQC to the end of May 2015, over 80% of GP services are rated either good or outstanding.
Poor care was being provided by 7% of those assessed, with 13% of hospitals and 10% of adult social care providers rated inadequate for safety.
The majority of services assessed by the CQC have been rated good, with some rated as outstanding, the report covering England said.
Leadership has been identified by the CQC as crucial, with 94% of good or outstanding services also rated good or outstanding for their leadership.
Among services rated inadequate overall, 84% were rated inadequate for leadership, the report The state of health care and adult social care in England 2014/15 said.
The report also called for providers to look at staffing in a "sophisticated" way focussed on quality of care, patient safety and efficiency, rather than just numbers and ratios.
Following CQC inspections, and subsequent re-inspections, half of providers were able to improve their ratings within six months.
Enforcement action taken against providers increased to 7% of inspections in 2014/15 from 4% in 2013/14.
David Behan, chief executive of the CQC, said: "The health and social care sector is facing an unprecedented level of challenge - so it's encouraging that our findings show that the majority of people are receiving good or outstanding care.
"We have found dedicated staff working hard to treat people with care, compassion and dignity.
"However, we have also found a wide variation in the quality of care people receive. Alongside good care we have seen examples of poor and unacceptable care and we rated 7% of care as inadequate.
"A key concern has been the safety of the care - a failure to learn when things go wrong, or not having the right number of staff in place with the right skills.
"Where people are not receiving the quality of care they deserve, we will demand action - and we are now able to demonstrate that half of services have improved following re-inspection.
"Some services may need further support to improve, and we will continue to work with partners to ensure this happens.
"The variation in care that we have observed is not just about the money. Good leaders are what make the difference - leaders who engage staff and people who use services and create a culture of continuous quality improvement.
"Leaders who have a broader vision than the delivery of care within their own organisations, but who work collaboratively with partners to innovate and transform services.
"What is very clear is that isolated working and incremental changes are not going to be enough to meet the challenges ahead."