A group of doctors has urged the main political parties to reconsider the way the NHS is funded.
A tax-funded NHS is unsustainable, say doctors
Politicians should look to move away from an entirely tax-funded system, says Doctors for Reform, a centre-right group set up two years ago.
The 900-strong group did not propose an alternative model, but said the health system was unsustainable in its current form.
But all three main parties said they were committed to a tax-funded system.
In a letter to the three main parties, Doctors for Reform said: "There is no doubt of the scale of the extra resources that have been put into the NHS... but it is equally clear that the extra resources have not created a service of the standard of our European competitors."
The doctors said there was a risk that under the present system the current climate of deficits and cuts could get worse.
More than 4,000 job losses have been announced in recent weeks as trusts struggle to balance their books.
And they added: "A mixed funding system with other sources of finance, equitably raised, would allow gaps in today's NHS service to be filled and a modern, truly comprehensive service to emerge."
And they added targets were undermining the bond of trust between doctor and patient.
Cancer specialist Karol Sikora, part of the Doctors for Reform steering committee, said: "The need for a more balanced funding system is urgent.
"Without it, rising expectations will be answered only by rationed services and longer waits."
The letter is not the first time doctors have called for a rethink of NHS funding.
Last year the then incoming Royal College of Surgeons president Bernie Ribeiro said patients should be forced to pay part of the cost of treatment as a tax-funded system was unsustainable.
He advocated a scheme of social insurance to cover the payments similar to the systems operating in France and Germany.
It comes as a poll of 1,012 people carried out for the Reform think-tank revealed two thirds of people believe the NHS in its current form was unlikely ever to meet public demands.
The British Medical Association, which represents 120,000 doctors, said it believed in a health system funded through taxation.
"What is important is that care is provided free at the point of delivery based on clinical need and with equal access for all."
And Nigel Edwards, director of policy at the NHS Confederation, which represents health service managers, said: "If a system is unaffordable through taxation, it is unaffordable through social insurance or whatever other system."
Karen Jennings, head of health at Unision, called the doctors "dangerous mavericks".
"It is totally irresponsible for these doctors to be making these dangerous, off the wall comments about NHS funding without any real evidence base."
And all three parties added they were committed to a tax-funded NHS at the moment.
Tory leader David Cameron ruled out a move to another system in his first major speech on health, while the Liberal Democrats are also committed to a tax-based system.
The government said it was "fully committed" to a tax-funded NHS.
And Prime Minister Tony Blair pointed out that while there was still much to be done, a tax-funded system had brought improvements in waiting times and cancer, cardiac and A&E care in recent years.