Researchers found men now earn much more if they decide not to go into schools after qualifying as a teacher, but instead take up posts in social services or healthcare.

Academics found that male graduates lost, on average, between pound;40,000 and pound;67,000 over their lifetimes after completing teacher training.

Women, by comparison, were found to be up to pound;65,000 better off if they stayed in the classroom, rather than being tempted into another similar job.

It is the first time academics have studied the pay gap between teachers who remained in the profession and those that left.

Peter Dolton, of the London School of Economics and Newcastle university, one of two academics behind the study, said: “The Government needs to make teaching a more attractive option and look at the wage structure of teachers over the course of their careers.

“A significant number of teachers are lost compared to other professions.

People are getting disillusioned and many can get more money if they move elsewhere.”

The study looked at labour force surveys from 1975 to 2001, analysing the wages of professionals with teaching qualifications who were no longer in education.

Professor Dolton, who carried out the research with Tsung-Ping Chung, from the LSE, said many qualified teachers worked in other public-sector jobs, such as the social services, or healthcare. Others had secured positions in administration, banking or clerical work after completing teacher training.

He said comparisons of these jobs with teachers’ wages showed there was little difference in salaries in the late 1970s but pay differentials have widened since then. The study showed women remained better off if they stayed in school, each earning between pound;42,000 and pound;65,000 more over their lifetimes. But Prof Dolton said the pay gap would have been considerably more 25 years ago.

Alan Smithers, of Buckingham university, in a separate study published this week, said that around 30 per cent of graduates successfully completing university-based teacher training courses are not in teaching the following March. He said the “shock” of working in the classroom was too much for many to bear.

Ministers will point to figures showing that there are growing numbers of teachers as evidence that the pay gap is not deterring people from entering the classroom. Teachers’ salaries have improved steadily under this government.

Teacher numbers have increased by 4,100 since 2003, bringing the total number to 427,700 - 28,500 more than in 1997 and the highest number since 1981.

But recruitment expert John Howson, a visiting professor at Oxford Brookes university, said: “There are some people for whom money is not a key factor. But you cannot rely on these people alone to fill all the vacancies we will have in the next 10 years.”