NICOLA Sturgeon has pledged to bring forward "credible, deliverable and affordable plans" to use Holyrood's new powers to protect poorer families from the UK Government's planned tax credit cuts.

However, the First Minister refused repeatedly to match Scottish Labour's promise to "restore in full" the money that 250,000 Scots households stand to lose.

Labour and the SNP again clashed over the issue during heated exchanges at First Minister's Questions.

Kezia Dugdale, the Scottish Labour leader, challenged Ms Sturgeon to reverse the cuts, which will costs families £1300 on average.

But Ms Sturgeon said: "What we will do as a responsible government is bring forward credible, deliverable and affordable plans to protect low-income households, just as we did on the bedroom tax.

"I think that, frankly, is a far better plan and it is far fairer for people who are affected by these cuts than back-of-a-fag-packet proposals from a party that knows it has little chance of ever being in a position to implement them."

Labour later accused the SNP of preparing the ground to partially, but not fully, compensate households facing tax credit cuts.

The row follows a U-turn by the SNP over welfare provisions in the Scotland Bill going through Westminster.

On Tuesday, the Nationalists claimed the legislation would not allow a future Scottish Government to top-up tax credit payments.

But 24 hours later, during a Holyrood debate on the issue, Social Justice Secretary Alex Neil conceded it would.

Ms Dugdale seized on the confusion during First Minister's Questions.

"This is the week the SNP's constitutional games came unstuck," she said.

"This is the week that the SNP had to confront the fact that difficult choices will have to be made, so will the First Minister now give up the politics of grievance, will she look to the future of what is possible, move on from the past and just get on with delivering a fairer Scotland?"

Scottish Labour has said it will not implement the SNP's planned cut in flight duty to help reverse the tax credit cut.

But citing a recent interview, Ms Sturgeon said Labour had already earmarked the £125million for education.

She said: "In the space of 24 hours Labour managed to spend the same sum of money twice over.

"That is basic incompetence and the people of Scotland frankly deserve better. It's less Keir Hardie, more Laurel and Hardy."