Ministers have dismissed as a "Marxist diatribe" a United Nations report calling on them to rethink a contentious change to housing benefit.
The UN's special investigator for housing, Raquel Rolnik, has urged the government to suspend cuts to what it calls the "spare room subsidy".
Ms Rolnik said the changes, dubbed the "bedroom tax" by critics, were eroding peoples' "right to adequate housing".
But housing minister Kris Hopkins said the report was "discredited".
Ms Rolnik was criticised by ministers after making a fact-finding mission to the UK last autumn, during which she appeared to question government policy.
The Brazilian said she had been invited by the UK government and devolved administrations to undertake a study into changes to housing policy but ministers disputed this and made an official complaint to the United Nations.
Since April 2013, social housing tenants deemed to have spare rooms have either had to pay more in rent or move somewhere smaller.
The government says it is removing subsidies which put social sector tenants in a better position than those in the private rental sector and the changes will free up living space for overcrowded families and help cut the £23bn annual bill for housing benefit.
But housing charities have warned that the result will be higher levels of rent arrears and greater homelessness.
In her report, Ms Rolnik said the UK must rethink whether the changes were having a disproportionate effect on the most vulnerable and were consistent with the need for a "fair and consistent" distribution of resources.
While she concluded that the policy did not, in principle, force anyone to move, she believed that many people with "no income to spare" did not have any other option to re-locate and this had left them in "tremendous despair".
She questioned whether the savings achieved would be outweighed by the economic and social costs of implementing the policy.
"The UN Special Rapporteur regrets that some policies and practices which have resulted in the progressive realization of the right to adequate housing are being eroded," she wrote.
"In particular, the removal of the spare-room subsidy should be suspended immediately and be fully re-evaluated in light of the evidence of its negative impacts on the right to adequate housing and the general well-being of many vulnerable individuals and households."
In response, the Department for Work and Pensions said the report was based on anecdotal evidence and its findings were "clearly written before any research was actually completed".
And housing minister Kris Hopkins added: "This partisan report is completely discredited and it is disappointing that the United Nations has allowed itself to be associated with a misleading Marxist diatribe."
Ms Rolnik, who visited council estates, food banks and homeless crisis centres during her visit, has said she will not be commenting further until the report is presented to the Human Rights Council in March.
But Labour, which has pledged to reverse changes to under-occupancy charge if it gets back into government, said the policy was "unfair and unworkable".