King's Fund says patients attending A&E are waiting longer and that the new system will be more complex than the old one

Cracks are beginning to appear in the NHS as "unprecedented financial pressures" begin to take their toll on the health service, according to a leading health thinktank in a mid-term assessment of the coalition's policy. The King's Fund warns that patients attending accident and emergency wards are waiting longer and that more hospitals are in financial difficulty. It says that if the NHS makes £20bn of savings in four years to March 2015, "year-on-year improvements in efficiency are required at a higher rate than any previously recorded".

Warning of "signs that the impact on patient care could be felt as early as 2013" from a combination of cuts and policy changes, the fund says that "the stakes could hardly be higher" with some hospitals "experiencing serious challenges in delivering services of an acceptable quality".

This theme is expected to picked up by health secretary Jeremy Hunt, who will launch the report with a speech outlining plans for Ofsted-style ratings for local hospitals focusing on the quality of care. Hunt will also say that NHS managers must be made accountable for the treatment patients get in the health service and that the government has asked the Nuffield Trust to come up with suggestions on how to measure the quality of care.

The report considers the government's health reforms and says that "major organisational changes and the loss of experienced managers leave the service in a precarious position". It also questions whether GP-led commissioning, the centrepiece of the reforms, will undermine the national system.

It warns that the clinical commissioning groups will take decisions at the local level "on whether to fund services … the reforms may increase inequity in access to services and create a significant postcode lottery".

Despite the coalition's claim that the new NHS will be more patient-friendly, the report says: "It is clear that the new system will be even more complex than the one it is replacing … With the dismantling of the old system nearly complete and the construction of the new one still under way, it is no exaggeration to say that the NHS is heading into treacherous waters, and the risks are high."

Andy Burnham, Labour's health spokesman, said: "This important report bears out Labour's consistent warnings that the government has placed the NHS in a precarious position. They have taken unacceptable risks with patient care by reorganising the NHS at a time of financial stress. Ministers inherited a successful NHS from Labour and, in just two years, have reduced it to a service that is demoralised, destabilised and fearful of the future."

However, ministers said: "The NHS must change so that patients can get the best treatment and care they need, when they need it."

Health minister Lord Howe said: "NHS care, particularly for older people, needs to improve. This is a priority for us, and we are clear that the NHS should make significant improvements in these areas. We are giving the NHS an extra £12.5bn. In the meantime, it continues to perform very well. As the King's Fund themselves say, waiting times are down, hospital infections are down, and mixed sex care is at its lowest ever levels."