The controversial so-called "bedroom tax" will be under the spotlight at the UK's highest court on Monday.
Supreme Court justices are to tackle the question of whether vulnerable members of society are being discriminated against.
During a three-day hearing in London a panel of seven judges, headed by Supreme Court president Lord Neuberger, will hear argument in a number of appeals resulting from legal rulings over changes to housing benefit regulations.
Campaigners say the regulations, introduced in April 2013, have had a ''devastating'' impact, and argue that they "unjustifiably" discriminate against the disabled.
The Supreme Court will hear a challenge by the Government against recent findings of the Court of Appeal in favour of a victim of domestic violence and the family of a severely disabled teenager.
Another part of the proceedings relate to an earlier decision made by Court of Appeal judges over a complaint by a number of appellants that the regulations unlawfully discriminate against people with disabilities who have a need for an additional bedroom because of that disability.
The High Court dismissed their application for judicial review and their subsequent challenge against that decision was rejected by appeal judges in February 2014.
In the latest "bedroom tax" case last month, appeal judges declared that a woman referred to as "A", who lives in a council house fitted with a secure panic room to protect her from a violent ex-partner, and Paul and Sue Rutherford, from Pembrokeshire, who look after 15-year-old grandson Warren, had "suffered discrimination", contrary to Article 14 of the European Convention on Human Rights (ECHR).
After announcing that the discrimination had not been "justified" by the Government, the judges said they were granting Work and Pensions Secretary Iain Duncan Smith permission to appeal to the Supreme Court.
The Supreme Court announced soon afterwards that the Government's appeal in the cases of A and the Rutherfords would be heard alongside other "bedroom tax" challenges already due to be considered by the justices arising from the earlier Court of Appeal decision.
The action brought by single mother A concerned the effect of the regulations on women living in Sanctuary Scheme homes which have been specially adapted because of risks to the women and children who live in them. The other, brought by the Rutherfords, involved the impact on seriously disabled children who need overnight care.
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 £480 million a year from the housing benefit bill.
In the 2014 ruling, Master of the Rolls Lord Dyson said the court could only intervene if measures were "manifestly without reasonable foundation" - and that test was not satisfied. The Secretary of State had "justified the discriminatory effect of the policy".
A DWP spokesman said in a statement before the latest round of the litigation: "Removing the spare room subsidy has restored fairness to the system for claimants as well as the taxpayer, and the numbers subject to a reduction are falling.
"We know that there are cases where people may need extra support – but rather than put in place complex exemptions, we have given local councils the freedom to decide what is best for their communities.
"That's why we have given councils £500m of funding to provide discretionary payments to those that need them, with a further £870m to be provided up to 2020."