Health secretary Andrew Lansley has said he was ready to accept “substantial and significant” changes to his NHS reform plans.

But Mr Lansley insisted that sticking with the status quo was “not an option”.

Without change, the NHS faces “enormous financial pressures” due to an ageing population and rising treatment costs which will spark “crisis” and undermine the health service, he warned.

By 2030, the number of over-85s requiring expensive health care is projected to reach 3.5 million, or one in 20 of the UK population, said Mr Lansley writing in the Daily Telegraph.

As a result, the NHS will have to perform an additional two million operations a year and health spending will double to £230bn - the equivalent of £7,000 a second - in real terms, a figure the UK “simply cannot afford”, he said.

Mr Lansley’s reforms have come under intense pressure from the outset, and more recently after deputy prime minister Nick Clegg made them a test of Liberal Democrat ministers’ ability to flex their muscles within the coalition government.

The legislative pause ordered by prime minister David Cameron to allow for further consultation comes to an end later this month, with the report of the NHS Future Forum. Mr Clegg has indicated Liberal Democrat MPs may vote against the Health and Social Care Bill unless proposed changes are watered down in response to the consultation.

In the article, Mr Lansley indicated his readiness to accept amendments to his plan and promised he would “never privatise our NHS”.

“We have always been clear that we are ready to accept any changes - substantial and significant - if they help us improve care for patients,” he wrote.

“When the Health and Social Care Bill comes back to Parliament, people should have every confidence that we will make the changes necessary to ensure the NHS is protected for our future generations.

“We will never privatise our NHS. But if we choose to ignore the pressures on it, the health service will face a financial crisis within a matter of years that will threaten the very values we hold so dear - of a comprehensive health service, available to all, free at the point of use and based on need and not the ability to pay.

“I will not allow that to happen.”

Mr Lansley said that the work of the NHS Future Forum, which brings together doctors, nurses and other health professionals, was “critical to getting our reforms right - right for patients, and right for the future of the NHS”.