Student loans in England should be written off for certain health staff once they have completed 10 years of NHS service, experts say.
The Nuffield Trust said the financial incentive was needed to stop a "dropout crisis" among nurses, midwives and other front-line staff.
It warned huge numbers were failing to finish training, or leave the NHS soon after starting.
But ministers rejected the idea, saying support was already in place.
The report by the Nuffield Trust is the most comprehensive look at what is happening to those who start training and begin their careers in the NHS.
It looked at a host of different groups from doctors and nurses to midwives and allied health professionals, including physios, occupational therapists and radiographers, who carry out scans.
This data is not routinely published.
But after analysing student records and employment trends, the Nuffield Trust found about one in eight trainee nurses, radiographers and occupational therapists failed to finish their training.
Those who did make it through training did not always go on to work in the NHS, and for those who did, close to one in five nurses, physios and occupational therapists left NHS employment within two years of starting.
