District hospitals obligated to bring in revenue "by whatever means necessary" will mean the government’s £20bn efficiency target will have to increase by an extra £10bn, it is claimed.
Dr Kosta Manis, a commissioning GP at Bexley CCG, predicted there will be "much steeper demands on the NHS" post 2015.
He said achieving £20bn worth of savings in the next four years is "utopian" and cited district hospitals as the barrier to meeting the target.
"The QIPP (Quality, Innovation, Productivity and Prevention) programme does not take into account changes in technology, demographics or anything else, so my guess is, it will be more like a £30bn savings target," he said.
"But even the thought of achieving £20bn worth of savings over the next four years, to me, is a utopia unless there is a drastic cut on district hospitals that are currently obliged to use any means available to bring in revenue."
According to a DH spokesperson, £5.8bn has already been saved under the QIPP programme this year.
DH National QIPP Advisor Dr Mahmood Adil said the government was "very much" on track to achieve £20bn efficiency savings in this parliament.
"Nobody expected we would get to £5.8bn but the wind is now behind us," said Dr Adil.
"We have developed a culture of quality and decreased costs."
Richard Douglas, Director General of Policy, Strategy and Finance at the DH, has been widely reported as claiming £50bn worth of efficiency savings will be needed by 2020.
Dr Adil said dates and targets would not be needed if the switch to a value based health system is successful.
"It is clear will still be facing the challenges of an aging population, advances in technology and increases in chronic diseases in the next decade and the following one thereafter," he said.
"We have already envisaged these pressures and acknowledge the need to move into a value based culture. If you implement that system, it doesn't matter what efficiency savings targets you have in front of you – you will achieve quality on reduced costs."
A spokesperson from the DH said they couldn't speculate what will happen to the QIPP programme post 2015.
"We will revisit the programme in the run up to the election and see if we need to extend it or not," they said.
"Savings are accumulative and recurring. If savings are made in the right way, they will continue beyond 2015.
"Increasing the savings target to £50bn by 2020 is one of the options."