David Cameron has clashed with nursing leaders over claims that the profession faces a recruitment crisis.
The outgoing chief executive of the Royal College of Nursing (RCN) Dr Peter Carter has warned that the NHS faces bankruptcy as nurses are "ground down" by working conditions and poor pay.
He also claimed that changes to immigration rules were restricting the supply of health workers.
The Prime Minister insisted there was a "massive" training programme for nurses and expert advisers had told the Government it was not an occupation which should be given special treatment under immigration rules.
Dr Carter told the RCN congress in Bournemouth that the profession was struggling to attract people into the job because of the pressures put on them by the staffing shortage and poor pay, leading to "patient suffering".
He said this would be worsened by immigration rules which will mean any non-European Economic Area residents must leave the country after six years if they are earning less than £35,000.
The RCN has calculated that up to 3,365 nurses currently working in the UK will potentially be affected, who will have cost the NHS £20.19 million in recruiting them.
If workforce pressures force a higher rate of international recruitment, the number of nurses affected could be 29,755, costing more than £178.5 million to recruit.
He said: "The nursing shortage is about to get even worse; in 2017 thousands of foreign nurses are going to leave the country.
"We know how few nurses earn more than £35,000. That's thousands of experienced staff committed to our health service, dedicated to the patients they care for being told to leave their homes in the UK.
"Across the country, health services rely on the good work they do, yet after spending time and money recruiting them, after investing time on their training, after supporting them to become valued members of staff, employers will have to let them go and find someone else to do their job.
"The Government must think again and make sure that nursing is not constrained by these illogical rules."
Dr Carter, who leaves the RCN at the end of July, said that these pressures were causing the recruitment crisis that was leading to massive agency bills because conditions and pay were not attracting enough people into the profession.
He said: "If there's one thing politicians need to focus on more than any other, it's the recruitment crisis gripping our health services.
"There's a simple reason why the agency bill is sky-high and in danger of bankrupting the health services, it's because there aren't enough nurses in the NHS."
He added: "Nurses are voting with their feet."
But Mr Cameron, speaking at an event in Runcorn, said he did not believe the immigration rules would lead to a shortfall of nurses.
" We have got a massive training programme for nurses at the moment, there are something like 8,000 more nurses in the NHS today than when I became Prime Minister. The training programme will continue," he said.
"But, crucially, we have an organisation called the Migration Advisory Committee and they advise us about which occupations to put on the so-called shortage occupations list, the ones where they fear skills shortages will develop. They haven't put nursing on that shortage occupation list and I think we should listen to their advice above all."
Dr Carter used his speech to criticise the decision by NHS England to suspend the safe staffing guidance developed by the health watchdog National Institute for Health and Care Excellence (Nice) in the wake of the Mid Staffordshire scandal.
He said: "In the build-up to the general election, hardly a day went by without promises of more money, more resources and, in particular, more nurses, and now is the time to hold those in power to account for these promises.
"Already one of the number one priorities is threatened. Nice has been told to stop its work on safe staffing guidelines. Stop delivering one of the key recommendations of the Francis report into Mid Staffs.
"After all the progress we have made, all the work we have done to highlight the importance of safe staffing, we are calling on secretary of state Jeremy Hunt and chief executive of NHS in England Simon Stevens to reverse that decision."
Explaining the growing pressures on nurses caused by austerity cuts, he said: "The years of cuts will take years to repair. This kind of problem is right across the UK, cuts to posts, downgrading, dilution of skills, resulting in caring compromises and patient suffering.
"Far too often nurses are held responsible when it's the systems that have failed and it's nurses that are picking up the pieces. This is totally unacceptable and totally unfair."