MUMS are being hit by a pay penalty if they work in part-time jobs, according to a new study published today.

Mothers tend to spend more time in part-time employment, so they do not benefit from pay rises associated with more experience, research found.

The report, funded by the Joseph Rowntree Foundation and published by the Institute of Financial Studies, states that the pay gap is partly explained by mums taking on part-time jobs and stopping paid work altogether while looking after children.

Childless women earn about 10 per cent less than men, but the gap increases “rapidly” for many women after they have children, the report says. Overall, mums earn about 30 per cent less on average than dads with a similar level of education by the time a first child reaches the age of 20.

IFS associate director Monica Costa Dias said that the government must understand the reasons why working part-time has “a long-term depressing effect” on wage growth so that the gender wage gap can be narrowed.

The overall gender wage gap has fallen from 28 per cent to 18 per cent since the early 1990s for those without a higher education but has remained at 22 per cent for those that have, the study reveals.

Chief executive of gender equality charity the Fawcett Society Sam Smethers, said: “What this study shows very clearly is that as a society we are not doing enough to value women’s talents. That is a blow to our productivity and a huge problem for the economy as a whole.

“We need to make it possible for part-time work to keep women on the career ladder. Employers should offer all roles, including more senior ones, as flexible working unless there is a good business case not to, and create more senior part-time roles.”

Joseph Rowntree Foundation chief analyst Helen Barnard said mums “pay a heavy price” for balancing part-time work and looking after their children as the poverty rate for part-time workers is double that for those who work full-time.

She said that bosses should increase the number and quality of jobs available on part-time hours rather than only allowing existing workers to negotiate a shorter work week.

In the mean time, Ms Barnard said, “as child poverty rises,” Chancellor Philip Hammond “should show he understands these pressures and ease the constraints facing low income part-time workers and their families by lifting the benefits freeze and fixing universal credit so families keep more of their earnings.”