Britain is suffering from a "hidden brain drain" of highly qualified women forced to slide down the career ladder after they have children, according to new research.

Almost half of professionally qualified women are downgrading to part-time jobs where the average employee is no more qualified than a 16-year old fresh from school, laying waste to years of higher education and experience.

"I am afraid what we found was pretty depressing," said co-author of the report, Professor Mary Gregory, an economist at Oxford University.

One in three female corporate managers saw severe downgrading after having a child, with two-thirds of that number taking clerical jobs rather than returning to top posts, the report published in the Economic Journal found.

But the worst-affected group of mothers were managers of shops, salons and restaurants.

Half of those women could only find work as sales assistants or similar low-level roles when they tried to return to work on a part-time basis after motherhood.

"You hear all sorts of horror stories," said Kate Lewis, Marketing and Communications Manager of Capability Jane, a company dedicated to finding highly skilled mothers appropriate flexible work.

"It's heartbreaking to hear of a real high-flier almost being forced to choose between her career and her home life and having to settle for something that isn't at the level they were used to operating at," Lewis said.

The report said it is socially inefficient to discard the talents and skills of women.

"Girls and young women are outperforming males at all educational levels. They are moving into an expanding range of occupations. The gender pay gap is narrowing. But for many this comes to an abrupt halt when childcare claims part of the working week," Gregory said.

The research, the first to quantify the extent of female brain drain, used two national databases detailing women's working lives dating back 26 years.

It followed 70,000 women from leaving school, their career path, having children, to returning to work.

The authors are calling for government intervention to make flexible working a given right, unless an employer can prove a strong case against it.

Capability Jane said it believed there are some small, positive changes happening in the British workplace.

Lewis said there is a current "war for talent" meaning larger corporations are more keen to hold on to their female talent.

Qualified mums are also finding flexible roles in small, fast-growing companies which can't afford such professionals on a full-time basis.

"Obviously this is not across the board, but we are finding that there are pockets out there who want female talent within flexible working," Lewis said.

Reuters