Disabled adults and families with disabled children are challenging the legality of the Government's so-called "bedroom tax", arguing that it unlawfully discriminates against them.
New housing benefit regulations have led to reductions in benefit payments to tenants in the social housing sector assessed to be under-occupying their accommodation.
Lawyers in 10 cases at London's High Court are seeking a ruling that the regulations, introduced on April 1, "unjustifiably discriminate against housing benefit claimants who are disabled or care for disabled family members".
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The PM faces a countdown to settle a deal before her minority government tries to get its Queen's Speech plans approved by the Commons.
More details will come today on proposals to offer EU residents the right to a new "settled status" in Britain after it leaves the bloc.
Scotland and Northern Ireland could see rain later but for the rest of the UK it should be a fine day.