The pay gap between male and female directors of companies and public bodies has widened, according to research by the Institute of Directors (IoD).

The study found that on average female executives were paid 22% less than their male counterparts last year, compared to a 19% pay gap a year earlier.

But for the whole working population, the gender pay gap has shrunk from 17.5% to 17.2%, according to figures from the Office of National Statistics.

Analysing the pay of about 3,500 directors, the IoD found that the service and voluntary sectors were the worst offenders in terms of pay disparities. In the service sector, male directors earned an average of £70,657, while their female counterparts were paid £56,933.

Pay differentials were lowest in the public sector, where the average pay gap was 5%.

The IoD said the basic pay of female directors had remained broadly unchanged last year, while male directors had often enjoyed significant pay rises.

IoD's director general Miles Templeman says: "Unless we can achieve equality of opportunity in the near future, we will inevitably face further regulation in this area.

"The only way to rebut this is for business to act quickly. It is wholly unacceptable in this day and age that it appears that women in comparable positions do not receive the same rewards as their male counterparts."