Labour has put further pressure on the Government's benefit cap after new figures showed around 20,000 families were affected by a policy ruled unlawful by the High Court.
New analysis from the Department for Work and Pensions shows 19,700 households affected by the benefit cap were single parents with children under the age of two.
Overall, 49% of the 88,000 households affected by the new lower cap were lone parents with a youngest child under five.
Shadow work and pensions secretary Debbie Abrahams said the lower cap "is pushing more children into poverty" and "punishing them for their parent's circumstances".
It comes two weeks after the High Court ruled the benefit cap is unlawful and illegally discriminates against single parents with young children under the age of two.
"As we warned, the impact of this and the Government's other social security cuts is pushing more children into poverty, punishing them for their parent's circumstances," Ms Abrahams said.
"The Government must listen to the High Court's judgment that this policy is discriminatory and unlawful, marking another blow in their failing austerity agenda.
"Labour has stood against the reduction of the benefit cap. We need to tackle our struggling economy, labour market inequalities and the high cost of housing rather than penalising children."
In November the cap, which limits the benefits paid to individual families, was reduced to £23,000 in London and £20,000 outside the capital.
Overall, single parents make up 63% of the 88,000 households affected.
The Government has indicated it will appeal against the High Court's decision, with figures released to Parliament saying it could spend more than £100,000 on legal fees at the High Court and Court of Appeal.
Ministers say the benefit cap encourages people back into work, the best way to lift them out of poverty.
But SNP MP Alison Thewliss this week led a debate in Parliament where she called on the Government not to appeal against the High Court's decision over a policy she branded an "injustice".
A Department for Work and Pensions spokesman said: "Work is the best way to raise living standards, and many parents with young children are employed.
"The benefit cap incentivises work, even if it's part-time, as anyone eligible for working tax credits or the equivalent under Universal Credit, is exempt.
"Even with the cap, lone parents can still receive benefits up to the equivalent salary of £25,000, or £29,000 in London and we have made discretionary housing payments available to people who need extra help.
"Since the introduction of the cap in April 2013, over 29,000 households who previously had their benefits capped have moved into work and are no longer capped."
Lone parents need to work for 16 hours a week to be eligible for working tax credits, and so be exempt from the cap.
The benefit cap will remain as it is while the appeal process is ongoing.
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