In a report published today, the Scottish Parliament's welfare reform committee concluded the cuts to housing benefit for people deemed to have surplus rooms were "iniquitous and inhumane".
SNP and Labour MSPs on the committee joined forces to demand powers to axe the policy, officially named the spare room subsidy, despite continued tensions over the Scottish Government's response.
Labour are pressing Scottish Government ministers to find ways to mitigate the impact of the benefit cut ahead of a final vote on the Government's Budget next week.
However, in an interim report published today, MSPs from both parties agreed thousands of tenants were "trapped" by the removal of benefit because they could not move to smaller properties.
MSPs found vulnerable tenants, including disabled people and children from broken families, were among the hardest hit.
They acknowledged it reduced the housing benefit budget but warned the policy "may cost more than it saves" by creating new costs for tenants, housing associations, councils and the Scottish Government.
The report, which follows a lengthy investigation, concluded: "The under occupancy charge, also known as the bedroom tax, is iniquitous and inhumane and may well breach tenants' human rights."
Michael McMahon, the Labour convener of the committee, said: "The bedroom tax remains bad law. The reality for many people is they cannot pay, and they cannot move.
"The only conclusion the majority of the Committee could come to, when faced with the evidence and research we have seen, is to call for the UK Government to abolish the bedroom tax with immediate effect.
"And if they won't do that, to give the Scottish Parliament the powers and resources to do so."
The SNP's Jamie Hepburn, the committee deputy convener, said: "The impact of the bedroom tax is having a real and harmful effect on people's lives, often the most vulnerable in society who deserve our compassion and support."
About 82,000 households have had spare room subsidies withdrawn as part of UK Government welfare reforms. Those deemed to have an extra room have lost 14% of their housing benefit, those with two extra rooms 25%.
The policy has cost affected households £50 per month on average. Four out of five households affected included a disabled adult and 15,500 of the total cases consisted of families with children, MSPs found.
The sole Conservative member of the committee, Alex Johnstone, refused to endorse today's highly critical report.
Labour says it will support the Scottish Government's Budget next week if Finance Secretary John Swinney finds a way to channel more cash to tenants struggling with rent arrears.
Yesterday Labour called on ministers to adopt schemes used in Renfrewshire and East Lothian to help tenants.
Speaking during First Minister's Questions, Alex Salmond said talks to find legal ways of mitigating the bedroom tax were continuing.
But he added: "However, every one of us knows that the way to defeat the bedroom tax and the rest of the impositions on the poor and disabled in Scotland is to take the powers over social security that Jackie Baillie alone seems to want to continue to have reside at Westminster."
Ms Baillie, Scottish Labour's social justice spokeswoman, said later: "Alex Salmond has again refused to accept there is a solution that is being implemented in parts of Scotland now."