Unions fear that nurse recruitment will be hit by the government's withdrawal of bursaries for overseas students on nursing diploma courses.
New guidance issued by the Department of Health brings in a three-year UK residence qualification for NHS bursary support.
Unison warned that withdrawing the£5,500 bursary from Irish students, in particular, would have 'a devastating impact' on future recruitment.
The union's head of nursing Karen Jennings said: 'We have always had a reciprocal arrangement between Ireland and England. We recruit a lot of nurses from southern Ireland.'
Unison had long called for student nurses to receive salaries rather than bursaries, in order to relieve the hardship that contributed to drop-out rates, Ms Jennings said. But the new guidance made the situation worse.
The row broke as statistics from the UK Central Council for Nursing Midwifery and Health Visiting showed the Philippines becoming the major source of overseas nurses and midwives for the first time, with 3,396 joining the UK register in 2000-01.
The figures also revealed that the number of nurses and midwives joining the register who had trained outside the European Union had increased 41 per cent in the past year, with 8,403 in 2000-01 compared with 5,945 in 1999-2000 and 3,621 in 1998-99.
Zimbabwe saw the number of its nurses coming to the UK increase by 73 per cent to 382, with Nigerian nurses up 67 per cent to 347 and Indian nurses up 201 per cent to 289.
Ms Jennings said: 'We recruit nurses from developing countries.'
But rather than drain developing countries of trained nurses, it was 'far better' to recruit students and train them.
'We ought to identify and ringfence money to allow us to recruit and train students from overseas. We should train nurses who will work here for some time and then return home, and we will be helping their countries.'
Royal College of Nursing association of nursing students chair Andrew McGovern said the RCN also had 'reservations' about the change. 'It is very inflexible at a time when the government's calling for more flexibility. The government is erecting a barrier to recruiting more overseas students.
'There are a significant number of Irish and overseas students recruited, particularly in London and the South East. It is over 50 per cent at some universities.
'It seems ironic that We are restricting overseas students from coming to the UK yet encouraging them to come when they're qualified.'
A DoH spokesman said:
'There is nothing to suggest these changes will mean there are fewer nurses being trained.'