Theresa May will vow never to allow the UK to become "looser and weaker'' in a speech ahead of a meeting in Scotland with Nicola Sturgeon.
'Proof' Welfare Reform Hits Poorest
Statistical "proof'' that welfare reform hits the poorest individuals hardest has been obtained by MSPs.
A study of the impact of welfare reform in Scottish electoral wards found people in some of the poorest areas lost nearly five times more money than those in more affluent areas.
The hardest hit area was impoverished Glasgow Calton, where adults lost an average of £880 a year, compared with adults in affluent St Andrews who lost an average £180 a year.
The Department for Work and Pensions (DWP) says its new universal credit "will make three million people better off - 300,000 in Scotland alone''.
Employment has increased by 48,000, unemployment has fallen by 10,000 and the number of people in Scotland claiming jobseekers allowance is 33,600 lower than 12 months ago, it added.
More than a dozen Glasgow wards figure prominently in the study among a list of worst affected places in Scotland.
The city is second to only Birmingham in terms of the overall scale of the loss, according to the research.
The study "demonstrates a clear relationship between the extent of deprivation and the scale of financial loss'', according to Holyrood's Welfare Reform Committee which commissioned the research.
It was conducted by Professor Christina Beatty and Professor Steve Fothergill from the Centre for Regional Economic and Social Research at Sheffield Hallam University.
Prof Fothergill said: "Scotland has not been singled out as the prime target for welfare reform.
"But as in the rest of Britain, the cumulative effect of the reforms is not only to hit some of the poorest individuals hardest but also to hit the poorest communities much harder than the most affluent neighbourhoods.''
Committee convener Michael McMahon, a Labour MSP, said: "Evidence that we have received indicated that our poorest communities are being hit hardest by welfare reform but we had no statistics to back this up.
"Now we have before us the evidence that proves it, right down to the electoral ward.''
More than £1.6 billion a year will be taken out of the Scottish economy with reforms to incapacity benefits resulting in the biggest financial losses, according to the research.
The Scottish average of £460 a year per adult of working age is broadly on a par with the British average of £470.
Prof Fothergill will give evidence to the committee on Tuesday followed by Scottish Secretary Alistair Carmichael on Thursday, and the committee has repeated its call for Work and Pensions Secretary Iain Duncan Smith to come to give evidence.
Mr McMahon added: "The UK Government cannot continue to refuse to engage on welfare reform. Not only do they refuse to undertake research like ours to assess the impact on people, but the relevant DWP minister continuously refuses to talk to us on the record and in public.
"We can ask the Secretary of State for Scotland about the stark data our research has revealed on Thursday but it is Iain Duncan Smith MP who should be giving evidence, rather than hiding from the impacts of his department's own policies. ''
Deputy convener Jamie Hepburn, an SNP MSP, said: "It is so depressing to see again in stark figures how the areas that most need support are those hardest hit by these reforms. Areas that already face challenges are simply having money sucked out of them.
"Even in areas like Edinburgh where the average loss is smaller, it equates to an estimated £130 million a year loss. This is money that should be supporting vulnerable people, and it should shame the UK Government to see this correlation between need and cuts.''
A DWP spokesman said: "The truth is employment is up, unemployment is falling and our vital reforms are working. We are returning fairness to the welfare system and helping people lift themselves out of poverty by making work pay. We are transforming the lives of the poorest people in society and bringing sense back to the welfare system - keeping the benefits bill sustainable, so that we can continue to support people when they need it most.
"DWP ministers have met with Scottish Committees in an informal capacity. The Committee is well briefed on the work we do and has taken up our offer to speak with a senior manager. As the Committee is well aware, DWP ministers already appear in front of the UK Select Committees as social security is a UK matter.''
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