The “motherhood penalty” is wreaking havoc on women and the economy, according to campaigners, as fresh analysis reveals that the pay gap between mothers and fathers in the UK has grown by nearly £1 an hour since 2020.

A study of the hourly earnings of mothers and fathers, released on International Women’s Day, found that on average mothers earned 24% less an hour than fathers in 2023 – a “motherhood pay penalty” of £4.44 an hour.

The analysis – which compares ONS data from January to March 2023 with the same period in 2020 – found that the median hourly pay was £18.48 for fathers compared with £14.04 for mothers.

And there are signs the situation is worsening, according to the campaign group Pregnant Then Screwed, which commissioned the analysis. It found the pay gap for median hourly pay between mothers and fathers had grown by 93p an hour since 2020, a 1.3% increase.

An increase in the cost of childcare and inflation since 2000 has made it “even harder for women to have children and earn a decent living”, said Joeli Brearley, the chief executive of Pregnant Then Screwed.

“These issues are silently eroding the careers of mothers, and unless they are prioritised by our government and by employers, this pay gap will continue to wreak havoc on women, families and our economy,” she said.

While the gender pay gap has been declining slowly over several decades, progress appears to have stalled in recent years. In 2023, the gap between full-time employees increased to 7.7%, from 7.6% in 2022, but decreased to 14.3% from 14.4% among all employees.

Caring responsibilities mean women often have to put their careers on hold and are more likely to work part-time – about 15% of men work part-time compared with about 42% of women, meaning the motherhood penalty accounts for almost all of the gender pay gap, said Brearley.

“It is a serious issue which ensures women have less power and autonomy than men,” she said. “It also contributes to rising child poverty – children aren’t poor by themselves, they are poor because their mothers are poor.”

According to analysis by the Institute for Fiscal Studies, the average earnings of men are “almost completely unaffected by parenthood”, but women’s earnings fall sharply after they have children and stabilise at a much lower level with little growth – seven years after the birth of a first child, women’s earnings are on average less than half of men’s.

The research, which comes ahead of Mother’s Day on Sunday, shows that in the first three months of last year, mothers earned 43% less than fathers (£442 v £769) based on median weekly earnings.

“Much as we all love breakfast in bed and a bunch of flowers, what women really want for Mother’s Day is quality affordable childcare, workplaces fit for the 21st century and an end to pregnancy discrimination,” said Jemima Olchawski, the chief executive of the Fawcett Society.