Liberal Democrats have sharply criticised their own government ministers for failing to stop the so-called bedroom tax.
Party members, gathered at the spring conference in Dundee, called on the coalition Government to defer the under-occupancy rules and reconsider its approach.
It came as protests took place across the country against the controversial policy.
Just one Lib Dem openly backed the Government policy at the end of a debate on the emergency motion on Saturday.
Former Lib Dem MSP Robert Brown, now a councillor, led the criticism, saying the change will mean a cut to people's "survival income".
He said: "I hope that conference will send the clearest of messages to the Government, to Liberal Democrat ministers, that the policy is damaging and unfair."
Another former MSP, Mike Rumbles, said he appreciates the party must make compromises in government.
"But taking an average £8 a week to encourage people to move to a smaller home is a nonsense," he said.
The policy is mean spirited, he told delegates.
The move follows the party's rejection of plans for "secret courts" in the Justice and Security Bill.
That decision was made on the day Deputy Prime Minister Nick Clegg made his keynote speech to conference.