Additional investment is delivering improvements in the NHS, a new report has concluded.

The Nuffield Trust found that £835 million of funding has been allocated towards quality-related initiatives within the National Health Service since 1999.

The authors reported a series of improvements during the first half of the government's 10-year plan.

But weaknesses were identified, including a lack of access to information to portray quality in a "comprehensive, fully-credible and defensible manner".

"Early data shows that the NHS is not broken," said report author Professor Sheila Leatherman.

"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."

Patients and staff should be more involved in the debate over the quality of NHS care, while an annual National Quality of Care report should be published, the report concluded.

"When trying to gauge quality in the NHS, it is difficult to see the wood for the trees," said co-author Dr Kim Sutherland.

"In our report, we have tried to bring together a range of data from different perspectives to develop a broad picture of quality in the NHS."

The findings were welcomed by health secretary John Reid.

"I welcome this independent report, which clearly shows that increased investment in the NHS over the last five years has produced improvements in performance," he said.

"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 plan."