A report said mothers are caught in a ‘Catch 22’, with childcare costs rising and statutory maternity pay falling.
The cost of childcare for parents with children under the age of two has increased by more than £2,000 a year since 2010, according to a new study.
The average annual nursery bill for a family with a toddler was £4,992 in 2010, but last year it was more than £7,200, said the union organisation.
The UK now has some of the most expensive childcare fees in the developed world, said the TUC.
A previous union survey of working parents with pre-school children showed that one in three spend more than a third of their wages on childcare.
The TUC estimated that parents with children under the age of two have to work 9.4 hours a week on average just to cover 25 hours of childcare at nursery.
Childcare fees have “shot up”, while statutory maternity pay has fallen in value since 2010, said the report.
TUC general secretary Frances O’Grady said: “Childcare should be affordable for all, but parents are spending a massive chunk of their pay packets on childcare bills, while their wages stagnate.
“This is putting huge pressure on family budgets at the same time as other living costs are shooting up.
“New mums are caught in a Catch 22. The UK’s miserly rate of statutory maternity pay means many are under financial pressure to return work early and are then at the mercy of sky-high childcare fees.
“We urgently need to get wages rising to stop households drowning in bills.”