New figures reveal for the first time the impact on Scots from George Osborne's cuts to in-work benefits through the new Universal Credit.

Critics have accused the Chancellor of attempting to resurrect his scrapped tax credit cuts by the back door.

Analysis shows that the average Scottish single mother-of-two working full time on the new National Living Wage would be £3,321 a year worse off by 2021.

The research by the House of Commons Library emphasizes the difference between those who remain on tax credits and those on Universal Credit, currently being phased in across Scotland.

Next year a single mother of two in Scotland working full time on the minimum wage would be an average of £2,981 a year worse off if they are on Universal Credit than someone in identical circumstances on tax credits.

Ian Murray, the shadow Scottish secretary, who asked the Library to calculate the Scottish figures, said: "This new research highlights the full and devastating impact that this Government's policies will have on some single parent working families in Scotland.

“Thanks to George Osborne's determination to fix the deficit on the backs of working people, many Scottish families on Universal Credit face the prospect of being significantly worse off."

He also accused ministers of creating a “perverse postcode lottery” of in-work support.

“This will leave families in some parts of Scotland far worse off than those in others,” he said.

The Conservative Government is currently rolling out Universal Credit across Scotland.

In Glasgow more than 3,600 households have already been transferred to the new benefit, compared to just 33 in Dundee and none at all in East Dunbartonshire and Moray.

Universal Credit is the brainchild of the Work and Pensions Secretary Iain Duncan Smith.

He has argued that too many people are trapped in a life on benefits and pledged to ensure that “work always pays”.

But the Chancellor surprised many with unexpected cuts to the in-work part of Universal Credit in his Budget.

Before Christmas the government’s own advisers warned Mr Osborne that he risked destroying the incentive to work and urged a U-turn.

The Social Mobility and Child Poverty Commission called on ministers to implement Mr Duncan Smith's original 2009 plan, under which those on Universal Credit would keep 45p of every extra £1 they earn.

Under the government's current plans, the Commission warned, that figure has fallen to 35p.

Universal Credit is designed to integrate six benefits, including in-work tax credits.

The Department for Work and Pensions (DWP) accused Labour of scaremongering.

The department claims that the UC cannot be compared to tax credits because the two systems are "fundamentally different".

Under Universal Credit, it argues, people are entitled to more generous childcare and "in-work progression support".

The system also avoid the "cliff edge" cuts to benefits if claimants take on extra work that exists under tax credits.

A DWP spokesman said: “This kind of scaremongering completely fails to recognise those who gain significantly under Universal Credit, and the fact that claimants are moving into work faster and earning more than under the old system.

“Universal Credit is fundamentally different to tax credits, and includes a wide range of additional support – including more generous childcare - that is not offered under the old system.”

Last month the DWP admitted that people on low pay would lose out under the Universal Credit system and suggested make up the money by working an extra 200 hours a year.

An official government response said: "We expect many claimants to respond to the changes announced in the summer budget by actively seeking more work, and we will support them with this.

"For example, someone could recoup the loss from the work allowance changes by working three to four additional hours a week at the national living wage to which they are entitled."

By 2020 2.6 million working families on Universal Credit are estimated to be on average £1,600 a year worse off due to the cuts to the work allowance in the benefit.