Holyrood could put a brake on post-Brexit trade deals struck by the UK if Holyrood is frozen out of negotiations affecting devolved powers, Mike Russell has warned.
The Cabinet Secretary for the Constitution today called for "formal mechanisms" to be adopted which would ensure the Scottish Parliament is involved from the start in any prospective deals involving countries like the US.
He claimed the Scottish Parliament is currently being "ignored" on the issue.
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"Scotland's devolved institutions have an important role to play in the negotiation and ratification of international treaties," he told MSPs today..
"The Scottish Government and the Scottish Parliament should be recognised as equals with the UK Government and Parliament in their respective areas of competence - with a presumption of interest and full, formal and early involvement in the process of making international agreements.
"Formal mechanisms must be established to ensure this parliament can carry out this role in scrutinising the mandate, negotiation and implementation of treaties."
He added that the consent of the Scottish Parliament should be secured before such treaties are entered into.
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Greens co-leader Patrick Harvie said MSPs should have the right to make decisions on all devolved matters. The mandate of treaties such as trade deals, impacting on devolved areas, should not be able to proceed without Holyrood's consent, Mr Harvie said
In addition a final text should not be adopted without Holyrood's approval, he went on, while the Parliament should also be allowed to change it's mind and withdraw consent if the "political balance" changes.
Mr Russell pointed to years of delays and hold-ups in finalising the CETA free trade deal between the EU and Canada after concerns among Belgian and Canadian provinces that their interests were being sidelined.
"There's a problem in the UK Government on the issue of how it looks at trade," Russell said.
"The United Kingdom, in seeking to exclude the devolved administrations in these matters is cutting off its nose to spite its face and will make it harder to take these issues forward," he warned.
The Cabinet secretary said it is essential that the UK Government recognises the role Holyrood has to play.
He added: "Presently they appear to wish to ignore that - that will be and is utterly unacceptable."