Chief executives and chairs of CCGs and hospitals said pressures to cut costs over the past 12 months had lengthened waiting times and restricted access to care. Most said these problems would worsen in the coming year.
The NHS Confederation report showed the NHS is struggling to adopt integrated models of care in the community.
The organisation's chief executive, Mike Farrar, said the 'sticking plasters on the creaking parts of the system will only last so long', and called for 'radical' changes to how the NHS operates.
The government said the NHS was doing well due to the hard work of its staff.
The NHS has been trying to save £20bn by 2014/15 as part of an 'efficiency savings' drive.
The poll, conducted for NHS Confederation by the Picker Institute, surveyed 185 chief executives and chairs of NHS hospitals, CCGs and other providers.
Half (50%) said financial pressures had affected waiting times and access in the past year, while seven in 10 (70%) expect waiting times to worsen in the next 12 months.
One in five (22%) of NHS leaders said financial conditions in the NHS were the worst they had ever seen. Eight in 10 (83%) said pressures would increase in the next 12 months.
Financial pressure is the most significant challenge facing the NHS over the next two years, they said.
Nevertheless, the survey found that 40% of chiefs said quality of care would improve over the coming year, although 32% said it would fall.
Only 8% said significant progress is being made towards a more integrated and community-based model of care. Over a third, 34%, said no progress had been made.
More than two-thirds (71%) said the government had not recognised the challenges facing the NHS.
Mike Farrar, NHS Confederation chief executive, said: 'In the short term the NHS is holding it together. But the sticking plasters on the creaking parts of the system will only last so long. We are already seeing the pressures on our A&Es bubbling over. Change is absolutely necessary if the NHS is to remain fit for the future – the risks of not doing so are simply too great to ignore.'
He added: 'Effective long-term change will require NHS leaders, with the support of the public and politicians, to take up the gauntlet and see through some radical changes to the way we deliver care. It is up to us all – NHS staff, the public, patients, government, and local and national politicians – to acknowledge the challenges and pressures we face and engage with delivering the solutions.'
In response to the report, health minister Lord Howe said: 'The NHS is performing well with waiting times overall low, satisfaction high and budgets overall doing well - this is testament to the hard work of NHS staff.
'We are looking at the pressures too and that is why through our Care Bill and other post-Francis measures we will help integrate services, drive up standards and make sure people get the care they need when they need it.
'We want to help dedicated, hard-working NHS staff do their good work. By protecting the budget and joining up services around the patient, we will do so.'