Parents are having to find up to £800 extra to cover the cost of childcare over the summer holidays, new analysis suggests.
Childcare costs rise during the school holidays when parents turn to holiday clubs or childminders while they are at work.
According to analysis from charity Save the Children, a parent with a three or four-year-old who usually receives 30 free hours of childcare could face an increase of between £530 to £832 during the summer holidays.
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The figures varies depending on where they live, with an average of £631 across England
They are calculated using the Coram Family and Childcare's Childcare Survey 2019.
The costs are based on a three or four-year-old using 40 hours per week of childcare and refer to the difference between term-time and holidays.
Families who are on Universal credit have to pay for childcare upfront.
But these costs are likely to increase during the school holidays, as parents are only entitled to free childcare hours during term time.
On Wednesday, seven mothers who have been pushed into childcare debt as a result of the policy will join Save the Children to lobby Parliament, demanding that changes are made to Universal Credit before it is rolled out nationwide.
A report from the charity analysed changes in childcare costs over the first four years of a child's life.
The research indicates that having to pay childcare costs upfront, both in the first month and on an ongoing basis, leaves parents facing regular shortfalls.
They are left to cover the cost out of their own pocket, having to use savings or go into debt.
Martha Mackenzie, Save the Children's director of UK poverty policy, said: "It is simply not right that families are being driven into poverty and debt by soaring childcare costs.
"Parents tell us it feels as if the system is stacked against them. They rely on childcare to go to work but when the school holidays come around they find themselves faced with sky-high childcare bills they can't afford.
"They are having to resort to desperate measures - cutting back on essentials, falling behind on bills or getting into debt - just to go to work."
A DWP spokesperson said: "Help with upfront childcare costs is already available, either through our non-repayable Flexible Support Fund or as a budgeting advance.
"We're committed to helping parents into work and those on Universal Credit can claim up to 85% of their childcare costs, worth up to £13,000 a year for families with two children."