Thousands of people have taken to the streets in protest at cuts to housing benefit for those with spare bedrooms.
Around 3000 people marched on George Square in Glasgow while up to 1000 people assembled outside the Scottish Parliament in Edinburgh, according to police estimates.
The protesters insist that the new UK Government policy will disproportionately affect disabled people and women, and could lead to evictions and deaths.
However, the rhetoric voiced at the rally took a trenchant turn, with Work and Pensions Secretary Iain Duncan Smith branded a "ratbag" and the coalition government compared to the Nazis.
The protest, entitled “Axe the Bedroom Tax”, was aimed at challenging an under-occupancy measure that forms part of the UK Government’s welfare reforms.
The change, part of the Coalition's welfare overhaul and shift to a universal credit system, will reduce the housing benefit received by those who have a spare room in their home.
The Coalition claims the policy will help tackle under-occupancy, and the knock-on effects on social housing waiting lists, by ending what it calls the "spare room subsidy" that sees tenants using housing benefit to live in properties that are bigger than their needs.
Opponents, however, have attacked the move as unfair and branded it a "bedroom tax", saying it will punish families who are already struggling.
Speaking in Edinburgh from a mobility scooter, disability rights activist Susan Archibald said: "We have heard talk about 'strivers and skivers'.
"One person can be a striver one day and then get made redundant. Will they be a skiver the next day? That's how easy it happens."
John McArdle, from anti-disability discrimination campaign Black Triangle, said: "Local man Paul Reekie, a contemporary of (Trainspotting author) Irvine Welsh and a good writer, committed suicide after a work capability assessment.
"10,600 people died last year within six weeks of their claim being ended unjustly by this fascist government.
"Every day our campaign receives more messages from desperate people who are on the brink of suicide.
"This Nazi government is killing disabled people, and we must stand together and say enough is enough."
Bill Scott, from disability campaign group Inclusion Scotland, said two-thirds of UK properties affected house a disabled person, rising to four-fifths in Scotland.
"The purpose of an equality impact assessment is to find out and then change your policy so it doesn't disproportionately impact on the vulnerable," he said.
"Instead, the UK Government went ahead and implemented that policy completely unchanged. It is a disgrace that this government chose to attack disabled people."
A spokesman for the Department for Work and Pensions (DWP) said: "It's only right that we bring fairness back to the system — when in Scotland alone there are 188,000 households on waiting lists and 60,000 living in overcrowded homes.
"We are giving councils £150m this year so that they can help their vulnerable tenants."
The DWP said it has provided councils with £150m in Discretionary Housing Payments to help people in difficult situations.
Foster carers and parents of armed forces servicemen and women are exempt from making the contribution, as are families with severely disabled children who are not able to share a room with a sibling.
Work and Pensions Secretary Iain Duncan Smith was branded a "ratbag" by a heckler during his visit to Edinburgh last week.
The insult was adopted liberally at today's march, with protesters wearing T-shirts and waving placards with the word "ratbag" superimposed over Mr Duncan Smith's face.
Kelly Parry, representing the National Union of Students, said: "He is a ratbag. The cuts that are going to come in are going to disproportionately affect women.
"We need to fight back so that never again will the people of this country be robbed by Westminster."
Alice Bowman, who is originally from the north of England but campaigns for the Radical Scottish Independence Campaign, said: "Only four out 45 Scottish MPs voted in favour of the bedroom tax. In an independent Scotland we will have our voices heard, and have control of our own budget."
A large number of Yes Scotland banners were paraded alongside banners from the pro-independence Scottish Green Party.
Ms Bowman was heckled by one protester, who said: "Alex Salmond could stop this tomorrow and he's not doing anything about it."
In a statement of support for the marchers, SNP MSP Linda Fabiani said: "The Scottish Government has brought in mitigation measures and has made a firm commitment to scrap the policy in an independent Scotland.
"SNP-led councils have committed to not evicting tenants affected by the bedroom tax, in contrast to several Labour local authorities who have refused to follow suit.
"There is no doubt that the bedroom tax is an abhorrent policy and the level of outrage surrounding what is being imposed is entirely justified."
View Rally against 'bedroom tax' -- Glasgow, 30 March 2013 in a larger map
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