As many as a quarter of student nurses in the UK quit their course before qualifying, figures suggest.
Many student nurses face financial pressures
Data obtained by Nursing Standard magazine under the Freedom of Information Act showed some courses have a drop-out rate as high as 50%.
The magazine calculated the high drop-out rate costs the NHS around £57m a year.
The government called the figures "rough estimates" that significantly exaggerated the problem.
There are no official figures as organisations collect data in different ways.
Sarah Poole, 38, from Havant, Hampshire, left her diploma at Southampton University after 18 months
She blamed a combination of financial pressures and poor experiences during practice placements.
She said: "I was ticked off by nurses for talking to patients - it seemed nurses were so hard-pressed they barely have to build up relationships with the people they are supposed to care for."
Nursing Standard requested attrition data from all 83 institutions across the UK that taught nursing courses between 2000 and 2004.
Of these, six universities refused to provide figures and 17 could not provide relevant data.
The figures received reveal that out of 19,995 nursing students who began degrees or diplomas expecting to finish in 2004, a total of 4,956 students dropped out - an overall attrition rate of 24.8%.
Drop-out rates were highest in London and the South East, and Scotland.
Northern Ireland has an attrition rate of 9%, and in Wales the figure was 17%.
Nursing Standard calculated that the failure of students to see out their course costs the NHS around £57m, based on each nurse costing around £11,500 a year to train.
Susan Watt, a student adviser to the Royal College of Nursing (RCN), told the magazine: "That is a huge amount of money.
"It is time to look seriously at this issue. It is also a waste of people resources."
The RCN blamed the high drop-out rate on financial problems, lack of childcare support, and poor experiences on wards and clinical placements.
It was also concerned some students were unable to cope with the academic demands of their course.
The lowest attrition rate - of just 7% - was recorded at the University of Huddersfield.
Barbara Wood, acting head of the University's adult and children's nursing department, told Nursing Standard that students were offered cheap accommodation, costing just £130 a month.
"We also prepare our students very well. Before they go out to work on wards, our students spend 32 hours in skills labs learning how to do useful tasks such as taking temperatures, toileting and bathing patients.
"That helps their confidence and also clinical staff's confidence in them."
Nursing leaders have warned the number of nursing students in the UK needs to double to replace those who will retire in the next 10 years.
One in four nurses in the UK is over 50 and 16% are over 55 and due to retire in the next five years.
Health Minister Lord Warner said the Nursing Standard figures were "rough estimates" that did not paint a true picture.
He said official figures collected by the Higher Education Statistics Agency for 2003-2004 put the attrition rate at 16% - a 2% drop on the previous year.
Lord Warner said there had been a substantial increase, both in numbers of nurses working in the NHS, and numbers entering training.
"We been working hard to make sure that all the extra nurses we've recruited stay in training and in work.
"For example by offering additional support to student nurses for the costs of childcare since April 2005, and improving pay, conditions and access to flexible working for those already working in the NHS."
Shadow Health Secretary Andrew Lansley said: "Before the election we made it clear we would consider enhanced bursaries for nurses during training.
"These figures highlight the need for this and the appalling waste of motivated students."
A spokesman for the Welsh Assembly said the most recent figure, for the academic year 2003-2004, showed the attrition rate in Wales for three-year degree courses was 9.2%.