The government's proposals to link teachers' pay to results have been described as "doomed to fail" by Professor David Guest, speaking at a conference organised by the Institute of Personnel and Development.

Professor Guest, Chair of Occupational Psychology at Birkbeck College, the University of London, said "performance-related pay is an old idea that has a lousy record".

The professor said that attempts to motivate public sector workers by offering higher salaries to higher performing staff were misguided.

"People do not go into the public sector because of the pay. But the government seems to be labouring under the misapprehension that they can still use pay to manipulate performance."

Union leaders such as Doug McAvoy of the NUT are opposed to performance pay

Prof Guest says that the evidence of research shows that performance pay "simply doesn't work".

This opinion is supported by long-term research published recently in the United States, which tracked a sample of academics who had worked within a merit-pay system.

The researchers from the universities of Missouri and New Mexico State found that there was little relationship between merit pay and subsequent job performance, suggesting that individual awards did not provide incentives to work more effectively.

The government has published a Green Paper outlining a new system for paying teachers which is designed to provide a higher salary for successful teachers.

An appraisal system will be introduced which will offer high-achieving teachers a 10% increase. There will also be extra payments for individual teachers and whole school staffs which are judged to have been particularly successful.

Teachers' unions have protested against the proposals, saying that they will be divisive and unfair. Instead they argue that there should be a substantial pay rise for all teachers which will raise morale and help to tackle the difficulties in recruiting new teachers.