Local government union Unison has demanded that maternity pay should be more than doubled so that new mothers are not forced back to work too early.
It says some women are cutting short their maternity leave or skipping meals because they cannot afford to live on the current statutory weekly amount of £172.48.
In a survey by Maternity Action on behalf of the union a quarter of women on maternity leave said they had gone without eating – sometimes all day – so that they could afford to feed their families.
The findings, released to coincide with Unison's annual women’s conference in Brighton this week, also show financial pressures are forcing new mothers to return to work sooner than they intended.
Results from the survey showed more than seventy per cent of women worried about money during their pregnancy or maternity leave.
Financial pressures forced more than half of new mothers to return to work before they were ready. Some had cut their leave to as little as six months because of money worries.
Unison general secretary Christina McAnea said: 'No mother should have to go without food or skip meals.
'But the failure of maternity pay to keep up with increasing living costs is driving many pregnant workers and new mothers into severe financial hardship.'
