The NHS is showing signs that it is getting better, a report from an independent think tank suggests.
In a 280-page document, the Nuffield Trust says there have been "many positive developments" since the Labour Party came to power in 1997.
However, it raises questions about the quality of care given to patients.
It says the impact of some of the government's reforms have not been measured and there is little way of knowing if they have improved care.
"When trying to gauge quality in the NHS, it is very difficult to see the wood for the trees," said Dr Kim Sutherland, one of the report's authors.
"There is a constant stream of reports and commentaries which are often contradictory in their interpretations and conclusions."
The report adds that doctors and nurses could play a greater role in improving the quality of patient care.
"The medical profession, although attentive to the Quality Agenda, is not yet sufficiently engaged and activated."
Nevertheless, the report's authors have praised the government's efforts to improve the NHS.
"This is the most ambitious, comprehensive and intentionally funded national initiative to improve health care quality in the world," said Professor Sheila Leatherman.
"Early data shows that the NHS is not broken. It shows capacity to improve.
"With the increased financial commitment and the 'quality' reforms in place, it is reasonable to expect that the NHS will continue to show significant progress in meeting the health needs of patients."
The government has spent millions of pounds on its quality reforms since coming to power. The report puts the figure at £835m.
It has set up a number of new organisations aimed at driving up the quality of care given to patients.
These include the NHS inspectorate, the Commission for Health Improvement, and the drugs watchdog, the National Institute for Clinical Excellence.
It has also introduced annual appraisals for doctors and new national service frameworks aimed at stamping out variations in the care given to children, the elderly, people with mental illness and those with serious diseases like cancer.
John Wyn Owen, secretary of the Nuffield Trust, said the reforms appeared to be working.
"The quality reforms implemented by the government are leading to improvements."
But he added: "To achieve the benefits of these initiatives, the authors recommend that specific actions be taken in the next 18 months."
These include the establishment of a new centre to assess the quality of care given to patients. It would produce an annual report to gauge whether services are improving.
They also called for greater involvement of patients and the public in the running of the NHS and measures to improve accountability.
Health Secretary John Reid welcomed the report.
"I welcome this independent report, which clearly shows that increased investment in the NHS over the last five years has produced improvements in performance.
"We still have some way to go, but we are making progress towards implementing the goal of a patient-centred service as set out in our own 10-year NHS Plan."