New figures from the UK have found that women earn on average 18% less per hour than male workers - this gap widens significantly if female employees give birth to a child.

In the 12 years after giving birth, this gap grows every year to an eventual difference of 33%.

While hourly wages do not fall immediately - the study shows these employees work fewer hours than their male counterparts. This contributes to them being overlooked for promotions and pay increases.

The study notes that woman with lower levels of education are hit hardest.

It concludes that men’s wages "tend to continue growing rapidly at this point in the life cycle, while women's wages plateau".

The Institute for Fiscal Studies (IFS) study also notes that the 18% gap is down from 23% in 2003 and 28% in 1993.

Robert Joyce, associate director at IFS, commented on the figures: "The gap between the hourly pay of higher-educated men and women has not closed at all in the last 20 years.

"The reduction in the overall gender wage gap has been the result of more women becoming highly educated, and a decline in the wage gap among the lowest-educated."

Corresponding Irish figures released last year showed that Irish women were paid an average of 14.4% less than their male counterparts in 2012 - this was an increase on a 12.6% gap in 2008.