Humza Yousaf has “fundamentally” rejected claims his predecessor failed to improve the lives of children.

And the First Minister said his Government’s defining mission is to reduce child poverty – amid concerns from Scotland’s outgoing Children and Young People’s Commissioner that “action isn’t following the words”.

Bruce Adamson took aim at the efforts of the previous administration – led by Nicola Sturgeon – to reduce the education-related attainment gap and alleviate child poverty.

The former first minister had said she wanted to be judged on education during her tenure.

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Asked on BBC Scotland’s Sunday Show if Ms Sturgeon had failed, Mr Adamson said: “Absolutely.”

He added: “I think all of us need to look at what we can do better."

Now Mr Yousaf has jumped to the defence of Ms Sturgeon after Mr Adamson said she had “absolutely” failed on the task.

Speaking to the PA news agency during a visit to the NHS 24 contact centre in Dundee on Monday, Mr Yousaf said: “I have the greatest of respect for the outgoing children’s commissioner, but I fundamentally disagree with Bruce Adamson about what he said about my predecessor or indeed what he is saying on the Scottish Government.”

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He said “game-changing” policies like the Scottish Child Payment, free bus travel for under-22s, and free school meals had been a defining legacy of Ms Sturgeon’s administration.

But looking to his own policies, he said: “I am the first to accept that more has to be done to reduce our child poverty rates in Scotland, which are too high.

“And that’s why I’ve made it a defining mission of the Government that I lead.”

Mr Adamson, speaking on BBC Scotland’s Sunday Show, said Mr Yousaf “may have made some big promises before becoming First Minister, but we’ve not seen anything on delivering those.”

He also raised concerns about the lack of movement on incorporating the UN’s Convention on the Rights of the Child (UNCRC) into Scots Law.

A Bill was unanimously passed by MSPs nearly two years ago but it was deemed by the UK Supreme Court to have overstepped the bounds of Holyrood and was struck down.

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Now, Mr Yousaf has committed to putting “pace behind” working with the UK Government on reintroducing the Bill – but he stressed the importance of not raising the Bill again in Holyrood until ministers were sure it would not be blocked.

He said: “I think part of his concern, of course, was that we haven’t made enough or sufficient progress in relation to the incorporation of the UNCRC, I think that’s fair criticism.”

He added: “Now we have to work with the UK Government when it comes to the re-introduction of that Bill. What I don’t want to do is reintroduce a Bill and there’s another referral, for example, to the Supreme Court.

“We are working with the UK Government and I’m going to put some pace behind that to make sure we can reintroduce that Bill sooner rather than later.”

Scottish Conservative shadow minister for children and young people Meghan Gallacher MSP said: “Humza Yousaf is trying to deny reality with his rejection of the outgoing Children Commissioner’s comments.

“While his remarks might make uncomfortable reading for the First Minister and his SNP colleagues, it was devastatingly accurate and cannot be ignored.

“During their 16 years in office, the SNP have let down our young people time and time again.

“Humza Yousaf should show some leadership, rather than burying his head in the sand over the failures of his party that were highlighted by Bruce Adamson.

“Only then will our young people have the best chance of prospering and receiving the support they need to succeed.”

Scottish Liberal Democrat Alex Cole-Hamilton said: "It is now very clear that when given an opportunity to distance himself from Nicola Sturgeon, Humza Yousaf is actively choosing to tie himself to her poor record.

"The Children's Commissioner's comments were measured and thoughtful. When he says Nicola Sturgeon "absolutely" failed, that should be the spur Humza Yousaf needs to do better.

"As a former youth worker myself, I know the magnitude of the challenges that are ahead in improving life for Scotland's young people. That doesn't mean the First Minister should stick his fingers in his ears.

"Instead he should bring back a fresh bill enshrining the UN convention on the rights of the child in Scots law, ensure routine reporting of adverse childhood experiences as recommended by the Burns review and get serious about tackling the educational attainment gap."