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.
SNP Call For Holyrood Tax Credit Powers
The SNP has called for the UK Government to devolve working tax credits and child tax credits in full as Scottish Labour challenged the Scottish Government to back plans to protect Scots from controversial cuts.
SNP MPs have lodged amendments to the Scotland Bill that they say would enable the Scottish Parliament to set its own tax credit system including eligibility, thresholds and tapers.
It comes as Scottish Labour leader Kezia Dugdale challenged the SNP to back her party's plans for protecting Scots from the UK Government's controversial tax credit cuts ahead of a debate at Holyrood.
MSPs will vote on a Labour motion that calls on the Scottish Government to use the new tax and welfare powers coming to the Scottish Parliament to restore tax credits to families north of the border.
Announcing the pledge at Scottish Labour's conference in Perth at the weekend, Ms Dugdale said it would be funded by not progressing with SNP plans to cut Air Passenger Duty by 50% before abolishing it altogether.
A future Scottish Labour government would also not increase the threshold at which people start to pay income tax at 40%.
The Scottish Government said it will bring forward plans to support those on low incomes following the UK Government spending review, and said "the first priority must be to stop cuts to tax credits completely''.
Ahead of the Holyrood debate, Social Justice Secretary Alex Neil said: "These Tory tax credit cuts will lead to an immediate £1,500 taken from the pockets of 250,000 Scottish working households next April and ultimately if all cuts are introduced, low income households could see a loss of £3,000 a year - so our first priority is to stop these plans altogether.
"Holyrood should send a united message to George Osborne that these cuts are completely unacceptable. Unlike Labour, the SNP have voted against these proposals at every possible opportunity and we will continue to do so.
"And just as we have already mitigated some of the worst aspects of the UK Government's welfare cuts, so too will the Scottish Government set out clear, credible and costed plans to support low income households following the Comprehensive Spending Review.
"In contrast Labour's plans fail even a basic test of credibility.
"The Labour leader has already promised to spend part of the proposed funding for tax credits on education.
"Labour are making empty promises to vulnerable people, that they know they will never have to deliver. That is neither credible nor fair.''
Ms Dugdale said the vote in the Holyrood chamber would be ``an important moment in the history of devolution''.
She said: "At long last everybody in Scottish politics is going to have to start talking about the responsibilities they do have, and how they would transform the lives of people in this country.
"If the SNP do not vote for this motion to restore tax credits it will confirm once and for all that the politics of grievance is more important to them than helping working families in Scotland.
"We know the powers to restore tax credits are coming and we know the money is there to fund them if people are willing to make difficult choices.
"Scottish Labour has been very clear about the choices we would make.
"The SNP say they are against the cuts and after weeks of dragging her heels Ruth Davidson agrees. It's now time for both to say what they would do differently.''
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