The NHS has achieved more than half of the efficiency savings challenge total and is on track to meet the £20bn target by 2015.
According to The King's Fund review of coalition health policy, more than £10bn of planned efficiency savings have been delivered through the Quality, Innovation, Productivity and Prevention (QIPP) scheme.
However, despite this the loss of "experienced" managers during the reorganisation of the NHS has left the service in a "precarious position" and "unprecedented financial pressures" are starting to bite.
It has been found 12 acute or ambulance trusts are performing "below par" in respect of finance, and 15 foundation trusts finished 2011/12 in deficit. Furthermore, there has been has been a rise in emergency admissions for people with long-term conditions, emergency bed days among the over-65s and in A&E waiting times.
The think-tank said it needed "more time" to judge the impact of the reforms on NHS performance but said the shift from targets and performance management under the last government has been "gradual", with much of the previous system still in place.
Anna Dixon, director policy at The King's Fund, warned neither competition nor commissioning reform alone can be relied upon to cope with the financial squeeze.
"The NHS is continuing to perform well but there are treacherous waters ahead," she said.
"There are huge risks, particularly in ensuring that quality of care does not suffer with the further financial squeeze. The stakes for patients could not be higher, and frontline leaders will have a crucial role to play in meeting the challenges ahead.
"Neither competition nor commissioning reform alone can be relied on to make the improvements needed. Fundamental change will be required to address the challenges of the future as the population ages and health needs change."
Dr Peter Carter, chief executive and general secretary of the Royal College of Nursing, said he believes there is a "real risk" of financial control being maintained "at the expense of patient care".
"We believe that both jobs and pay increases for staff are vital for the future of the health service," he said.
"To achieve this, we need bold leadership to reshape how services are organised and clear reinvestment of the efficiency savings currently being made in England."
The think-tank also claimed it is "too early" to judge the impact of government policies in areas such as the reduction of health inequalities and improving patient experience as much of the data is "not yet available".
However, it does note health care-acquired infection rates continue to fall, with MRSA rates dropping by 42% and C difficile rates by 55% from May 2010 to September 2012, and praised the government's "good progress" in eliminating mixed sex wards, with the number of breaches falling by over 96% in 16 months.