Governments are failing to invest in women and girls and, as a result, are missing out on billions in economic gains, according to a new UN report.

This year’s Gender Snapshot report from the UN Women agency found that the global cost of failing to educate young women adequately is an annual $10tn (£7.6tn); low- and middle-income countries will lose $500bn over the next five years if they do not close the gender gap on internet use; and improving support for female farmers could add $1tn to global GDP. It also found that at current rates child marriage could continue until 2092.

Papa Seck, head of UN Women’s research and data section, said: “The cost of not achieving gender equality is just way too high but at the same time, the potential returns of doing so are also too high to ignore for societies.”

The annual report, which assesses progress of gender equality across the UN’s sustainable development goals (SDGs), also found that 47.8 million more women than men face moderate or severe food insecurity; that it could take a further 137 years to end extreme poverty for women; and that climate change could force 158 million more women and girls into poverty than men and boys.

Governments must “start investing hard cash into women and girls”, said Seck, and make “non-negotiable” changes to their laws to better protect them.

No country has all the laws needed to prohibit discrimination, prevent gender-based violence, uphold equal rights in marriage and divorce, guarantee equal pay and provide full access to sexual and reproductive health, the report found.

Of the 120 countries where data is available, more than half have at least one restriction preventing women from doing the same jobs as men and half do not classify rape as based on a lack of consent.

In the UK, Rachel Saunders, an expert in women’s legal issues at Nottingham University, said the government should create new laws that mandate employers to share staff salaries and allow women to know if there is a sex offender in their area.

She said that even when such laws did exist, many were not fully implemented. For example, the Equality Act 2010 is meant to protect UK citizens from workplace discrimination yet Saunders said the gender pay gap persisted and that there was still an expectation for women to take parental leave rather than offering both parents an amount to split.

Jemima Olchawski, chief executive of the Fawcett Society, which campaigns for gender equality, said there was a general complacency that viewed gender disparities as “ghosts” from a time when women did not have the rights they had today and an attitude that things would naturally improve over time.

“That is absolutely not the case,” she said. “We are consistently and constantly perpetuating and even creating new inequalities for women and girls.”

Elsewhere, she said women continued to experience “absolutely horrendous situations”, citing the Taliban’s ban on Afghan women working, studying and even speaking in public.

“I’m not at all surprised to see that, sadly,” Olchawski said. “We’re just not seeing progress.”

Ezel Buse Sönmezocak, advocacy officer for Women for Women’s Human Rights, a Turkish equality campaign group, suggested that governments should fund feminist moments “because we know that when you [do], you build a defence against backsliding.” The snapshot, she said, should be a signal “to hold on to the SDGs and be more ambitious”.