Relying on overseas nurses to staff the NHS is a short term solution that cannot be sustained, the Royal College of Nursing has warned.
Many overseas nurses work in the NHS
Nearly half of all new nurses currently come from abroad, a new report commissioned by the RCN shows.
At its annual conference in Harrogate, the RCN urged the government to step up investment in UK nurses.
Secretary General Beverly Malone said it was impossible to guarantee foreign nurses would continue to want to come.
She said: "UK employers are now starting to face stiff opposition from other countries such as the US and Canada who have their own nursing shortages.
"Nurses from overseas make an invaluable contribution to the UK's health care system.
"In fact, without them, in terms of nursing numbers, we would have been running fast just to stand still.
"But we can't guarantee that these nurses will continue to want to come to live and work in the UK. Nor should we encourage the targeting of nurses from developing nations.".
The reliance on non-UK nurses has increased year on year since the mid 1990s.
The UK is the most heavily reliant of the western nations on nurses from developing countries.
Sandra James, a nursing manager from Guernsey, told the conference that she had been to the Philippines to recruit 30 nurses three years ago.
"This is all about money, let's not con ourselves," she told delegates.
"I found myself asking myself what I was doing and whether I was doing anything different from the people who do people trafficking."
The RCN says if this trend continues at the current rate, the supply of nurses from countries such as the Philippines and South Africa may not be able to keep pace.
New sources, such as the former Eastern Block countries that joined the European Union on May 1, may then be targeted, it said.
Recruitment from certain developing nations is banned to safeguard their healthcare systems.
But as the ban only applies to the NHS, recruitment agencies and independent sector employers are still free to recruit nurses from these countries.
To compound the problem, the number of UK-trained nurses leaving the country to work abroad has increased. More than 8,000 nurses left the UK between 2000/1-2002.
Dr Malone believes a new pay and career package in the NHS - Agenda for Change - would solve many of the recruitment and retention problems.
She said: "Investing in our future workforce by increasing student bursaries and by including nurse educators in Agenda for Change negotiations would all have a positive effect."
Liberal Democrat Shadow Health Secretary, Paul Burstow MP, said the figures were a wake up call for the government.
"Overseas recruitment is their sticking plaster solution to the nurse recruitment problem.
"It is morally indefensible to aggressively recruit nurses from developing countries with their own health crises.
"It is also not a long-term solution to rely on overseas nurses to the detriment of UK recruitment.
"Other developed countries like the US are also competing for the same pool of nurses. We need to grow our own and keep our own nurses in the UK".
Tim Yeo, for the Tories, said: "This is a worrying but unsurprising report which confirms our long-held concerns about the dangers of relying too heavily on the recruitment of overseas nurses and not doing enough to attract and retain home grown talent.
"We are especially pleased that it highlights the unacceptable practice of unethical recruitment.
"If the government has nothing to hide on this issue, it should ban the NHS from using recruitment agencies which have not signed up to its own code of practice."
Health Secretary John Reid told the conference the NHS must recruit ethically.
"I am not complacent. The progress is still not good enough," he said.
"We need to do more and work in partnership with developing countries.
"We will update the code of practice so that there will be no mistakes whatsoever."