The Court of Appeal has upheld the legality of Government cutbacks in the benefits system that campaigners say are pushing people "to breaking point".
Christian leaders have warned that "cutbacks and failures" in the system are forcing thousands of people to use food banks.
But appeal judges have ruled that two of the Government's most controversial cutting measures - the so-called "bedroom tax" and the benefit cap - are not unlawful.
Lord Dyson, Master of the Rolls, rejected a two-pronged legal attack and said the court could only intervene if the measures "were manifestly without reasonable foundation".
The judge ruled that that test was not satisfied and both challenges must fail.
Later campaigners vowed to fight on, saying the cuts are having a "devastating" impact on vulnerable people.
The Department for Work and Pensions, which was a defendant in both legal actions, welcomed the court's ruling.
A spokesman said of its bedroom policy: "We are pleased that the courts have once again found in our favour and agreed our policy is lawful.
"Reform of housing benefit in the social sector is essential to ensure the long-term sustainability of the benefit. But we have ensured extra discretionary housing support is available for vulnerable people."
"The benefit cap sets a fair limit to what people can expect to get from the welfare system - so that claimants cannot receive more than £500 a week, the average household earnings."
Lord Dyson sat with Lord Justice Longmore and Lord Justice Ryder to hear the bedroom challenge. In a separate hearing, he considered the legality of the benefit cap with Lord Justice Longmore and Lord Justice Lloyd Jones.
The bedroom regulations, introduced in April last year, have led to reductions in housing benefit payments to tenants in social housing assessed through controversial "size criteria" to be under-occupying their accommodation.
Tenants with one spare bedroom have had a payment reduction of 14% and those deemed to have two or more spare have seen a reduction of 25%.
Campaigners say the regulations have had a "devastating" impact on many people by imposing an "excessive and unfair burden" and failing to reflect the needs of disabled people for extra space because of their health problems.
The DWP rejects the ''bedroom tax'' tag and says the reality is that ''a spare room subsidy'' has been removed from social sector tenants.
It says the Government's aim of reducing rising housing benefit expenditure is lawful and legitimate, and an ''integral aspect'' of its deficit reduction programme. The change in regulations is expected to produce savings of £500 million a year.
In the benefit cap case, it was argued the Government's flagship cutbacks policy is having a particularly harsh impact on women fleeing domestic violence, and on their children, threatening to trap them in abusive relationships.
The case was brought by two lone parents forced into temporary accommodation in London, and one each of their children.
The cap forms part of Government reforms to reduce spending on welfare by £11 billion per year.
Lawyers for disabled people affected by the spare bedroom policy said they were "baffled" by today's ruling as it fails to provide legal protection for people with disabilities.
The National Housing Federation's head of policy Kevin Williamson said the launching of court action shows "how desperate" disabled people are.
He said: "Disabled people across the country are being forced to cut back on food and heating to pay the bedroom tax.
"The Government said discretionary housing payments would protect them but one in three disabled people who applied for it were turned down."
Lawyers for lone parents affected by the benefit cap say the court is supporting a measure that is likely to have "not only devastating consequences for individual children but serious financial costs as the fallout impacts on other public services, including social services, education and the justice system."
Ugo Hayter, from law firm Leigh Day, representing two of the disabled appellants, said an appeal to the Supreme Court was under consideration, adding: "We are extremely disappointed by this judgment and we are baffled by the findings of the Court of Appeal."
Mr Hayter said: "Our thoughts go out to the thousands of disabled tenants who continue to be faced with uncertainty, poverty and the risk of eviction."
Anne McMurdie of Public Law Solicitors, whose company acts for three of the appellants, said: "The Government has sought to make savings by targeting the most vulnerable in our society. On the Government's own figures at least 440,000 disabled households will lose out under the new regulations.
"There is compelling and growing evidence of the terrible adverse impact on disabled tenants, having to make the dreadful choice between paying the rent and buying food or heating their homes.
"Disabled tenants are not asking for extra funds - they are asking for housing benefit to be paid at a level which meets their needs - for the same right as others. Discretionary payments are not the answer."
Richard Kramer, deputy chief executive of Sense, the national deafblind charity, said: "We are extremely disappointed with today's decision by the Court of Appeal on the legality of the bedroom tax.
"We know from our experiences of supporting deafblind people that the bedroom tax has adversely affected disabled people. Many have been found to have a so-called extra bedroom despite requiring it because of their disability, for example needing extra space to store disability-related equipment and for short-term carers.
"Many disabled people, including the deafblind people that Sense supports, have been pushed to breaking point. They are struggling with the transition from DLA (Disability Living Allowance) to PIP (Personal Independence Payment) and many are facing huge cuts to their social care, leaving them without the support they desperately need to live full and active lives.
"Alongside other benefits being cut, housing benefit has been the final blow for many disabled people and can lead to serious financial hardship.
"We are urgently calling on the Government to reconsider this unfair policy and to prevent disabled people from suffering financially as a result of their disability."
Richard Hawkes, chief executive of the disability charity Scope, described the appeal ruling as " a setback for the campaigners and a major blow for the 400,000 disabled people who are feeling the impact of this policy".
Mr Hawkes said: "We've spoken to disabled people who aren't able to share a specially adapted bed with their partner, and have to sleep in a separate room.
"Disabled people are being forced to move, or find the extra cash they don't have to pay their rent."
Rebekah Carrier, of Hopkin Murray Beskine Solicitors, who represented the benefit cap appellants, said they also hoped to take their case to the Supreme Court.
Ms Carrier said: " In particular it is disappointing that the court declined to decide important issues of principle affecting the large numbers of women and children made homeless by domestic violence every year.
"The Government promised to address this in April 2013, 10 months ago, but has failed to do so. The court recognised the problem and expressed concern about the Government's delay in addressing it, but they have abandoned many domestic violence victims to their fate until the Government chooses to act.
"That is not good enough for my clients, or for the many women who will face a stark choice about whether to stay with a violent partner, or flee and risk losing their home or being destitute."
Among the test cases is that of Charlotte Carmichael, from Southport, Merseyside, who says she is unable to share a bedroom with her husband, Jayson.
Other challenges awaiting the outcome of today's hearing include those launched by separated parents, who say they need room for children when they come to stay, and victims of domestic violence rehoused with special security.
Since the High Court hearing, disabled children have been given exemption from the "bedroom tax".
The death of grandmother Stephanie Bottrill has been blamed on the tax. The Sunday People reported that the 53-year-old threw herself into the path of a speeding lorry after having to find an additional £80 a month in "tax" when her two children both left home.
The newspaper reported that she left a suicide note to her son, Steven, 23, saying: "Don't blame yourself for me ending my life. The only people to blame are the Government."
Later Mr Bottrill said he had discovered that she should have been exempted under the regulations as a long-standing tenant.
© 2014 Press Association