Single parents with children under the age of two have won a High Court challenge against the Government's controversial benefits cap scheme.
The action was brought by four claimants over the "failure" to exempt them and their dependents from the scheme.
A judge said the claim related to the "revised" benefit cap which requires the parent to work at least 16 hours per week to be exempt.
"Real misery is being caused to no good purpose," the judge said as he announced his ruling.
He added that he was "satisfied that the claims must succeed" against the Work and Pensions Secretary.
Mr Justice Collins said: "Whether or not the defendant accepts my judgment, the evidence shows that the cap is capable of real damage to individuals such as the claimants.
"They are not workshy but find it, because of the care difficulties, impossible to comply with the work requirement."
"Most lone parents with children under two are not the sort of households the cap was intended to cover," the judge added.
What is the Benefit Cap?
The benefit cap is a limit to the total amount in some benefits that working-age people can receive
The cap is set at £23,000 per year for families inside Greater London and £20,000 outside
For single adults in London, it is £15,410 and £13,400 per year outside of London
Certain exemptions apply, and specifically in relation to lone parents, they have to work for at least 16 hours a week at minimum wage
Rebekah Carrier, a solicitor for the claimants, said: "Single mothers like my clients have been forced into homelessness and reliance on food banks as a result of the benefit cap.
"We are pleased that today's decision will relieve my clients - and other lone parent families around the country - from the unfair impacts of austerity measures which have prevented them from being able to provide basic necessities for their children."
The judge has given the Government permission to appeal against his ruling.
In statement, a Department for Work and Pensions spokesman said: "We are disappointed with the decision and intend to appeal.
"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."
They also said Discretionary Housing Payments were available to people who need additional help.
Alison Garnham, chief executive of the Child Poverty Action Group, said: "We hope this case is the beginning of the end for this nasty policy.
"It is a policy that punishes the vulnerable for being vulnerable and even fails on its own terms."
"We have the ridiculous situation where one part of the DWP has been telling lone parents with very young children that it understands they should not be expected to work, and another part of the DWP is punishing them severely for exactly the same thing," she added.