Chris Ham, chief executive of healthcare charity the King’s Fund, said the situation reflected “the increasing pressure hospitals are under to maintain good standards of patient care, access in A&E, short times to get operations done, short cancer waits and balance their budgets at the same time”.

He said the worry for government must be that financial problems were spreading beyond “the usual suspects” and that “many more hospitals are now in that position”.

Asked if some hospitals would run out of money, he said: “There is a real risk of that this year and particularly next year.”

In 2015/16 about £2bn from the NHS budget will be put into the Better Care Fund, intended to help the NHS and local councils provide more integrated health and social care

“It’s a good idea,” said Mr Ham. “But it’s money that would have gone to paying hospitals so they’re having to find even bigger efficiency savings to balance the books and deliver good standards of patient care. That’s a very, very big ask.”

He said hospitals that were part of foundation trusts might be able to draw on reserves for the short term, but those that were not would have to ask the government for more money.

“There needs to be a longer-term resolution of the funding issues facing the NHS because, after four years of no growth in the budget, it’s hard to see where the savings will come from.

“The impact is already being felt on patient care. We need an honest discussion [about] how much more money [is needed and] where will it come from to ensure the sustainability of the NHS that we all value so highly.”

Anita Charlesworth of the Health Foundation think-tank said the NHS had been “doing well” during austerity and had managed to make savings.

But she said: “There is a ‘pincer’ – as the NHS takes on more nurses, drug prices are rising and their pension costs are rising, as part of government policy.”

And she warned: “We’re not going to find this money behind the sofa, so it really would mean the Treasury stepping in.

“If it can’t do that, we’re faced with cutting services and cutting quality.”

‘Gap after savings’Meanwhile, an estimate by the health regulator, Monitor, underlines the possible scale of the challenge.

It says there is a funding gap of just over £5bn for 2015-16 in the NHS in England’s £78bn commissioning budget for all secondary healthcare – which makes up about three quarters of its total budget and includes hospitals and mental health services.

Even after all realistic efficiency savings are made, Monitor says, a deficit of £1.6bn will remain in this section of the budget.

The concerns over the NHS budget in England come after recent research by the Nuffield Trust suggested the NHS in Wales was facing a £2.5bn funding gap over the next decade.

Health minister Mark Drakeford said that report, commissioned by the Welsh government, recognised long-term savings could be made if services continued to be reformed.