Prime Minister David Cameron has been urged to halt the roll-out of universal credit after new powers are devolved to the Scottish Parliament.
Deputy First Minister Nicola Sturgeon made the call on the Conservative MP given the policy, which combines six different benefits into one, has already been delayed.
Universal credit is being phased in across the UK by 2017 and is already available to some claimants in Inverness.
The legislation effectively abolishes housing benefit which is likely to be devolved to Holyrood.
The Scottish Government has questioned how there could be a meaningful discussion about devolving a welfare benefit that is already in the process of being scrapped.
Ms Sturgeon said UK Work and Pensions Secretary Iain Duncan Smith told the Conservative conference this week that the roll-out of Universal Credit across the UK was to be “accelerated”.
“It is hard to see how this is in any way consistent with a good faith approach to the process of agreeing more powers for the Scottish Parliament,” she said.
“There is a widespread consensus that the Westminster parties’ proposals on the devolution of welfare powers are far too timid and that the Scottish Parliament needs substantial control of the welfare system to help people into work and tackle the growing scandal of poverty in Scotland.
“However, it is hard to see how even the limited welfare proposal of the main Westminster parties – to devolve control of housing benefit – can be delivered if the UK Government presses ahead with Universal Credit.
“I have therefore written to the prime minister today asking that the roll-out of Universal Credit – which in any event is already significantly delayed and discredited – is halted in Scotland.”
Ms Sturgeon, who hopes to replace Alex Salmond as first minister, said it was essential that the Westminster parties respect the process of agreeing more powers in “actions as well as words”.
“There is already concern that Westminster wants to backslide on the promises made before the referendum,” she added.
But the Conservatives, Labour and Liberal Democrats have insisted they would keep their word.
Former Prime Minister Gordon Brown has vowed to do “everything in my power” to ensure meaningful devolution takes places.
He has called for 14 new powers to be devolved to Holyrood, covering borrowing, welfare, the Crown Estate, employment rights, health and safety, equality, income tax and an assignment of a share of VAT revenues, among other areas.
Mr Brown said: “I think No voters will now understand that I will do everything in my power to ensure that the change they voted for is delivered with no ifs, no buts and no damaging conditions attached.”