An SNP minister has admitted her administration is investigating “extending” devolved powers so that flawed legislation to protect children’s rights is deemed legally competent.

The Scottish Government has suggested that officials are looking at whether the devolution settlement can be expanded to accommodate the incompetent piece of legislation if efforts to redraw the Bill are a failure.

Last year the Scottish Government lost a benchmark Supreme Court case over legislation passed at Holyrood that was designed to incorporate the UN Convention on the Rights of the Child (UNCRC) into Scots law.

The court ruled that parts of the Bill were incompatible with the Scotland Act and outside of Holyrood’s powers.

The ruling was also jumped on by opponents as a potential pretext for a potential legal tussle over Holyrood’s authority to hold a referendum on independence without UK Government approval.

Children’s Minister Clare Haughey has stressed the Scottish Government is “urgently and carefully considering the most effective way forward for the legislation”.

She said: “Our preference is to address the Supreme Court’s judgment by returning the Bill to parliament via the reconsideration stage.”

But she added: “In parallel with planning for that, we are also exploring options for extending our powers to incorporate the UNCRC beyond those that are available under the current devolution settlement.”

SNP ministers have now been accused of attempting to “ramp up their grievance machine” against the UK Government, with unionist parties calling on the Scottish Government to stop using the legislation as a “political football” and focus on ensuring a path is found for children’s rights to be embedded into Scots law.

Deputy First Minister John Swinney, who is leading on the Bill, has penned a letter to Scottish Secretary Alister Jack stating that the Scottish Government is “working on amendments that can be made to the Bill within the current competence of the Scottish Government”, which will be discussed with UK officials.

He added that the Scottish Government’s “preference” is to “find a way to enact the Bill as originally passed by Scottish Parliament”.

Mr Swinney said: “So we have also identified potential routes to increasing the effectiveness of incorporation, beyond those that are now available to the Scottish Parliament alone.

“These include ensuring that UK acts in devolved areas – such as education – are subject to the UNCRC and that the Scottish Parliament can make all legislation within its legislative competence meaningfully subject to international human rights standards.

“In the meantime, we are planning to return the Bill to the Scottish Parliament for reconsideration.

“We are currently considering very carefully how to deliver UNCRC incorporation to the maximum extent possible within the limits of the devolution settlement as now clarified by the Supreme Court’s decision.”

But, in response, Mr Jack has warned that the Scottish Government’s plans “could imply significant changes to the devolution settlement.”

He added: “I feel it is important to be clear at the outset that the UK Government’s position is that the current devolution settlement strikes the right balance, and that amendments to the Bill and any other proposals would need to be within the parameters of the devolution settlement as it stands”.

Scottish Conservative shadow constitution secretary, Donald Cameron, said: “Far from apologising over their appalling approach to this bill, we now have an SNP minister talking up yet another illogical strategy.

“The nationalists have been playing games with the vital subject of children’s rights for far too long. Their focus should be on making the necessary changes as urgently as possible to pass this bill.

“Ministers still seem determined to ramp up their grievance machine rather than engaging with the UK Government to ensure this piece of legislation can proceed properly.”

Scottish Labour’s human rights spokeswoman, Pam Duncan-Glancy, said: “It is becoming clearer by the day that the SNP are playing politics with children’s rights, choosing constitutional arguments over the incorporation young people have spent so long fighting for.”

“These comments from the minister raise more questions than they answer, casting fresh doubt on when this landmark legislation will finally be delivered.”

She added: “This is far too important to be used as a political football, or a point scoring exercise.

“The SNP’s failure to make any progress on this is nothing short of shameful – they must put children first, allow them the full realisation of their rights and get this bill fixed and in place as a matter of urgency.”

A UK Government spokesman said: “Protecting vulnerable children is a priority for the UK Government, one we share with the Scottish Government, and it is for them to consider the next steps on their legislation.

“The Scottish Secretary was clear that the current devolution settlement strikes the right balance.

“Any amendments to the UNCRC Bill or other proposals would need to be within the parameters of the devolution settlement as it stands.”