THE UK Government has launched a legal challenge against landmark child rights legislation passed unanimously by the Scottish Parliament.

In a move branded "morally repugnant", legal officers say MSPs may have gone beyond the parliament's powers.

Nicola Sturgeon has called the move "jaw-dropping" while John Swinney has warned UK ministers: "If the Tories want to target the rights of Scottish children, then they can expect to see us in court."

The UK Government believes parts of two Holyrood bills impinge on Westminster sovereignty. One incorporates the United Nations Convention on the Rights of the Child (UNCRC) into Scots law and the other does the same with the European Charter of Local Self-Government.

Both received cross-party backing in the Scottish Parliament last month.

But the Supreme Court will now rule on their competence.

If the court finds against the legislation, it can send it back to MSPs to make changes.

READ MORE: UK Government is accused of political ‘grandstanding’ over children's bill

The news met with strong condemnation from supporters of the reforms.

But the UK Government has insisted its concerns "are not about the substance of the legislation, rather whether parts are outwith the legislative competence of the Scottish Parliament" - in disagreement with Holyrood's Presiding Officer.

In a letter to Swinney last month, Scotland Secretary Alistair Jack (below) said the UK Government had "concerns" about the legal obligations that the UNCRC bill "could be seen to place on UK Government ministers in reserved areas".

The National:

He wrote: "The bill would affect the UK Parliament in its power to make laws for Scotland, which would be contrary to the devolution settlement.

"The UK Government respects the Scottish Government’s right to legislate on this matter in line with its responsibilities under the devolution settlement. What it cannot do is seek to make provision that constrains the UK Parliament’s ability to make laws for Scotland."

Today Swinney said: "The bill is a massive shift in power out of the hands of ministers and into the hands of children themselves.

"It builds children’s rights into the fabric of decision-making in Scotland as every devolved body, every health board, every council and the Scottish Government itself will be legally obliged to make sure they respect children’s rights.

"And, it means the courts can order action wherever they find children’s rights have been breached.

"Not a single voice in the parliament was raised against the bill. It passed unanimously.

"And, crucially, it has been certified independently by the presiding officer as being within the powers of the Scottish Parliament.

"Now, the Tory Westminster government is trying to veto those rights. That is not just morally repugnant but it is also deeply menacing.

"The only people who need fear this bill are people who want to breach children’s rights.

"The only people who want to block this bill are people who know they are already breaking those rights.

"If the Tories want to target the rights of Scottish children, then they can expect to see us in court."

Posting on Twitter, Nicola Sturgeon called the move "jaw-dropping", saying: "The UK Tory Government is going to Court to challenge a law passed by @scotparl  unanimously. And for what? To protect their ability to legislate/act in ways that breach children’s rights in Scotland. Politically catastrophic, but also morally repugnant."