NHS Providers chief executive Chris Hopson told the BBC's Andrew Marr Show on Sunday that hospitals were increasingly unable to cope within existing resources.
He called for an urgent discussion on rationing of NHS services, warning that without a rapid increase in funding for the health service, providers could be forced to cut staff, charge for services or stop providing some services.
Delivering the government's election pledge to create a seven-day NHS, he warned, was simply impossible within existing resources and with existing levels of staff.
The NHS Providers chief's comments came just days after a leading think tank reported that almost half of hospital trusts predicted a year-end deficit, along with more than a quarter of CCGs. His remarks were welcomed by the GPC.
GPC deputy chairman Dr Richard Vautrey told GPonline: 'It was good to hear Chris Hopson being so clear about the financial and workload challenges facing the NHS and the impossibility of expanding and already overstretched service.
'This is something GPs know all too well and it's vital that the government starts to take this more seriously, moves away from political soundbites around seven-day services and properly funds general practice and the wider NHS to deliver the current service for an expanding and increasingly ageing population, let alone try to do more.
'Patients don't want cuts to their NHS services and so it comes to a political decision to invest properly, and at comparable levels to other European counties.'
A DH spokesman said: 'On the back of a strong economy, we are giving the NHS the £10bn it asked for to fund its own plan for the future - including almost £4bn this year to transform services and improve standards of care. We know the NHS is under pressure because of our ageing population, but we rightly expect the service to continue to ensure that patients get treated quickly.'