Britain's top businesswomen were paid nearly a fifth less than their male counterparts this year, even though they worked longer hours, a survey showed.

The annual pay survey by the Institute of Directors showed the average salary of a female company director was #60,000 this year, about 19 per cent less than the #74,028 earned by male directors.

The gap has narrowed from 24 per cent since last year, but female managing directors are working longer hours than their male counterparts.

Those employed in small or medium-sized companies put in an average of 51.25 hours a week compared with 50 hours for men.

In larger companies, women directors worked an average 57 hours a week, while their male colleagues clocked up 55, the survey of 1,000 firms showed.

"The pay gap has often been justified on the basis that women work shorter hours. Our survey refutes that suggestion," said IoD director general Miles Templeman.

The IoD's findings echoed official data last week that showed there was still a 12.6 per cent discrepancy between women's and men's pay in the year to April, although it was the smallest since records began nearly 40 years ago.

The IoD said the gender pay gap was wider in the private sector, where female directors' earnings were just #55,000 compared with the #74,440 paid to the men.

In the voluntary sector, the average salary of women directors was #47,840 versus #64,500 for men.