Politicians need to be braver when it comes to putting the case for change in England's NHS, particularly over service closures, health leaders say.
Mike Farrar, of the NHS Confederation, which represents managers, said there had been a "chronic failure" so far.
He said politicians had been putting short-term electoral interests first.
And he warned if the issue was not addressed the health service could find itself in real financial difficulty and patients would suffer as a result.
Mr Farrar was speaking ahead of the confederation's three-day annual conference which starts later in Manchester.
The group also released details of evidence they had collected from more than 250 NHS trust chief executives and chairman.
It showed many believed the health service was facing a very serious financial situation with some describing it as they worst they had ever experienced.
Many also predicted it would get worse without radical change, such as hospital closures and mergers and greater integration with community services, which can keep costs down by helping patients manage their conditions.
Mr Farrar said the NHS was doing well in meeting its financial challenge - it has been asked to save £20bn by 2015.
But he said if the health service was to thrive in the long-term it needed politicians to show more leadership.
"The NHS is like a super-tanker heading for an iceberg. The danger is clearly in view and looming ever larger.
"It is clear that what the NHS desperately needs is public support for planned change to services.
"But politicians have consistently failed over many years at national and local level to put the long-term interests of their population's health above their short-term electoral interests."
Health Secretary Andrew Lansley said he accepted the NHS was facing a financial challenge, but said standards of care remained high.
He also said the health service had the full backing of this government in pursuing changes.
"The NHS needs to change to match the needs of a changing population.
"We will not shy away from difficult decisions involved in that."