The High Court has been asked to declare that the government's so-called "bedroom tax" unlawfully discriminates against disabled people, in ten cases brought to illustrate the serious impact of the regulations up and down the country.
New housing benefit regulations, introduced on April 1, led to reductions in benefit payments to tenants assessed to be under-occupying their accommodation.
Under new "size criteria", tenants with one spare bedroom have had a payment reduction of 14% and those deemed to have two or more spare, a reduction of 25%.
Human rights lawyers say that, unless the families move from their homes into smaller properties, they face building up rent arrears and being forced out any way.
Among the 10 claimants challenging the bedroom tax is Jacqueline Carmichael who lives with her husband in a two-bedroom housing association flat in Stockport.
She is severely disabled with spina bifida and has to sleep in a fixed position in a hospital bed with an electronic pressure mattress.
Mr Carmichael cannot sleep in the same bed as it is not large enough for two and his movements at night could cause her harm.
There is not enough room for a second bed so he sleeps in a separate bedroom.
But the couple's housing benefit has been reduced by 14%. They have been granted a discretionary payment to cover the shortfall in their rent for six months but do not know how they will meet it when the period ends, say their lawyers.
Mr Carmichael is a full-time carer for his wife, and if he were to take a job to make up the difference she would face going into residential care.
Disabled widower Richard Rourke, from Whitwell, near Worksop, Derbyshire, has had his housing benefit reduced by 25% on the basis that he has two bedrooms spare. A wheelchair user, he is now building up rent arrears.
He has a disabled stepdaughter at university who suffers from a rare form of muscular dystrophy and needs one of the rooms when she comes home during holidays and at weekends.
The other room is a box room he uses to store essential equipment, including a hoist for lifting him, a power chair and shower seat.
He says there are no two-bedroom properties available locally in the social rented sector suitable for wheelchair use, and no suitably adapted properties in the private sector.
He is still waiting to hear whether he is eligible for a discretionary housing payment.
Another applicant, James Daly, from Stoke, is the father of a severely-disabled son who stays with him every weekend and at least one day during the week, as well as part of the school holidays and when his mother is away.
Separated from his wife, Mr Daly occupies a two-bedroom flat but is deemed to be over-occupying the property by one bedroom - his son's room.
Mervyn Drage is a single man from Manchester who has lived alone for 19 years in a three-bedroom flat in a high-rise tower block, on the site of a former colliery.
The property was originally built for miners but was let to him because the local housing authority considered it unsuitable for families.
He suffers from mental health problems, including depression, anxiety and obsessive compulsive disorder (OCD) and has various physical problems.
He does not sleep in his any of his three bedrooms. All contain papers he has accumulated over the years, as does his bath.
His lawyers say his medical condition is exacerbated by stress and changes to his routine and is now very anxious about the prospect of having to move because the new regulations mean he can no longer afford to live in the flat.
Applicant JD, from Birmingham, is a full-time carer for her 26-year-old daughter who has severe physical difficulties, learning disabilities and blindness.
They live in a three-bedroom property specially adapted to meet the daughter's needs. There is a spare room because the daughter's brother has moved out, leaving them caught by the new regulations.
Family lawyers say the home is extremely important to the daughter, referred to as AD, and it would be difficult to manage her transition to a new home.
There are fears a move would have a significant impact on her psychological, emotional and behavioural well being.
Another family who remain anonymous consist of a husband and wife with two children aged six and two living in a two-bedroom flat in south London on the third floor of a block of flats.
Their six-year-old son is disabled and they need to move, but their lawyers say if they are allocated a home which actually meets family needs their housing benefit will be cut on the basis that they will be "under-occupying", even though the allocated property is appropriate to their needs.
Another family among the 10 includes a single mother whose ex-partner assaulted her six-year-old son, leaving him traumatised.
After the partner was jailed, she was allocated a three-bedroom property because of her son's behavioural and mental health issues.
She received a letter from her local authority telling her that her housing benefit was being cut by £15.52 a week because she was under-occupying.
Applicant Ms T and her husband live in a one-bedroom flat with two sons, one of whom has autism and the other Downs Syndrome.
The couple's lawyers say their flat is damp and infested with mice. The child with autism sleeps in the bedroom and the parents sleep with the other child on the living room floor.
Because of the boys' conflicting needs, they have been assessed by their local council as needing three bedrooms, but if they move in to suitable accommodation they will not be able to afford it under the regulations.
Dinner lady Mrs N lives in London with two children, including a son who is autistic and violent towards his sister and has a room of his own. About three years ago Mrs N left her violent partner.
She works as a dinner lady but is now anxious "with awful memories of the time when she was homeless because of violence" that she will have to move because of the spare bedroom regulations.
Her lawyers say the children are well settled at their local school, but she cannot work more hours or take in a lodger to meet the shortfall in rent that would be caused by the loss of benefits.
In a three-day hearing, he is asking the court to rule that the new regulations breach Article 14 of the European Convention on Human Rights, which protects against discrimination.
He also argues that Iain Duncan Smith, the Work and Pensions Secretary, has failed to comply with his public equality duty under the 2010 Equality Act and the discriminatory element in the regulations must be quashed.
The Department for Work and Pensions (DWP) rejects the "bedroom tax" tag and says the reality is that "a spare room subsidy" has been removed from social sector tenants.
DWP lawyers say reduction of rising housing benefit expenditure is an "integral aspect" of the Government's deficit reduction programme, and the change in regulations is expected to produce savings of £500m a year.
They say that quashing the regulations would have a "significant impact" on this aspect of public expenditure.
In written submissions to the judges, they argue the DWP has acted lawfully and given careful consideration to the impact of housing benefit laws upon a wide range of groups of people, including the disabled, and made a judgment on what is "the best distribution of limited resources".