The Scottish Parliament has refused to rubber-stamp controversial benefit changes linked to Iain Duncan Smith's welfare reform programme.
It is the first time Holyrood has taken such a position on Westminster legislation, and it followed an appeal by Scottish Health Secretary Nicola Sturgeon for MSPs to take a stand.
She conceded that the move - prompted by the proposal for universal credit and personal independence payments - will not stop the Welfare Reform Bill being passed at Westminster.
But it will lead to the Scottish Parliament agreeing its own legislation dealing with areas where the Bill affects devolved issues, including free school meals and the blue badge scheme for disabled drivers.
Scottish Labour backed the SNP's call to refuse the necessary Legislative Consent Motion (LCM) on part of the Bill, voting this afternoon on a motion to reject it by 100 votes in favour to 18 against.
But the move was criticised by Tory and Liberal Democrat MSPs who defended their coalition colleagues south of the border.
Ms Sturgeon said: "This will be the first refusal of legislative consent in the lifetime of this Parliament.
"The fact that it's not a blanket refusal shows that we don't take it lightly.
"But it is right that we in this Parliament stand up for the most vulnerable in our society."
She argued that Westminster should be able to legislate on areas of the Bill covering data-sharing, industrial injuries disablement benefit and the Social Mobility and Child Poverty Commission.
Ms Sturgeon, who is also Deputy First Minister, said she supports efforts to simplify the benefits system.
But she said measures put forward by Mr Duncan Smith amount to cost-cutting.
She said: "We recognise that the welfare system is broken and needs to be fixed, but we will not endorse proposals that seek to fix it at the expense of some of our most vulnerable people."
She said benefits receipts in Scotland would be reduced by £2.5 billion by 2015, with £1 billion coming from disabled people and their families.
Ms Sturgeon accepted that welfare reform is an area of responsibility held by Westminster, not the Scottish Parliament.
But she added: "Though these reforms are not of our making, we and the people of Scotland will be paying the price of them for a very long time to come."
Scottish Labour health spokeswoman Jackie Baillie said the UK Government's reforms were the "single most significant attack" on the welfare state in her lifetime.
"The starting point for this reform is not about fairness or supporting people back into work - it is purely about saving money, often from the most vulnerable people in our communities," she said.
But she added that there are also challenges for the SNP administration in Edinburgh, adding: "They have known about the UK Government's intentions with the Welfare Reform Bill for almost a year, yet even the most basic questions about what the Scottish Government will do have yet to be answered."
Scottish Tory health spokesman Jackson Carlaw said the SNP and Labour at Holyrood had brought forward a "hollow blank canvas of lurid rhetoric".
He added: "Nothing we do today will alter the course of the UK Welfare Reform Bill, and to suggest otherwise is to deceive those affected and to give quite false expectations to those whose circumstances will change."
Lib Dem MSP Liam McArthur said: "At best, it seems to be a gesture, but one with potentially serious consequences."
A Department for Work and Pensions spokeswoman said: "We are pleased that the Scottish Government recognises the welfare system needs urgent reform so it's fair, simpler and that work always pays.
"These reforms will end the cycle of generations of Scots living a life on benefits whilst ensuring that those people who need our help and support get it unconditionally. When one in five Scottish households is workless, something fundamental needs to change."