A victim of domestic violence and the grandparents of a severely disabled teenager have won court of appeal challenges over the lawfulness of the bedroom tax. 

Three judges at the court of appeal in London ruled in their favour on Wednesday following a hearing in November.

One case, which was brought by A – a single mother living in a three-bedroom council house fitted with a secure panic room to protect her from a violent ex-partner – concerned the effect of the policy on women living in Sanctuary Scheme homes.

The other, brought by Paul and Sue Rutherford, involved its impact on seriously disabled children who need overnight care.

In both cases it was argued that the policy, which came into force in April 2013, unlawfully discriminates – against women and domestic violence victims and against children in the situation of the Rutherfords’ grandson, Warren.

The government rejects the term “bedroom tax” and says the regulations remove what is in fact a “spare room subsidy”, with the aim of encouraging people to move to smaller properties and save around £480m a year from the housing benefit bill.

The lord chief justice, Lord Thomas, Lord Justice Tomlinson and Lord Justice Vos announced that they were allowing the appeals in both cases on the ground that the “admitted discrimination in each case … has not been justified by the secretary of state”.

The Department for Work and Pensions (DWP) was given permission to challenge the court of appeal’s ruling at the supreme court.