THE Welsh and Scottish Governments have launched a formal dispute over Theresa May's power-sharing deal with the Democratic Unionist Party (DUP).
As part of the coalition deal Northern Ireland was guaranteed an extra £1 billion.
But, despite the other devolved nations usually being entitled to an equivalent amount of funding under the Barnett Formula, Westminster has claimed this does not apply.
Wales and Scotland's finance secretaries have argued under the two countries should be entitled to £1.67 billion and £2.9 billion respectively.
The Welsh Government's finance secretary Mark Drakeford said: "We have been clear with the UK government that any additional funding for Northern Ireland must respect the established funding principles and rules around the Barnett formula."
He added: "At a time when public services in Wales are under pressure as a result of the UK Government’s damaging and ongoing policy of austerity, it is only right that Wales gets its fair share of funding."
Speaking in Parliament earlier this week Torfaen MP Nick Thomas-Symonds said the move was "hardly likely to strengthen the union".
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