Scottish secretary David Mundell has branded Nicola Sturgeon "ridiculous" over suggestions that Tory right-winger Jacob Rees Mogg could "trample all over" devolution, as the Brexit row intensifies.
The Tory MP has now suggested that more "maturity" is needed to reach a breakthough in the deadlock over the repatriation of powers from Brussels after Brexit.
The Scottish Government says that Westminster is effectively legislating to take control of dozens of powers which should belong at Holyrood over key areas like farming and fishing.
Ms Sturgeon suggested in a weekend article that in future this could mean "Jacob Rees Mogg as Prime Minister, trampling all over Holyrood's authority and rolling back devolution.". But this was dismissed by Mr Mundell as he appeared before Holyrood's devolution committee today
"I think remarks that Jacob Rees Mogg is suddenly going to start imposing regulations and rules in Scotland - at a point only two weeks after this parliament acknowledged that a large section of the welfare responsibilities for Scotland had been devolved to it and that it would be able to create its own welfare system - are frankly ridiculous.
"The Government's track record - this Government, previous coalition governments - on devolution is one that I am proud of."
He added "I think one of the signs of the maturity in relationships between Parliaments is that we are able to disagree - and of maturity in relationships between Governments when we're able to disagree - but still continue to have a dialogue,"
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The Scottish Secretary also told MSPs that Scottish Government Brexit minister Mike Russell was not making any decisions when it came to seeking a deal on Brexit.
He said that "very constructive discussions" took place with Mr Russell at the Joint Ministerial Committee this week aimed at resolving the deadlock between Holyrood and Westminster over powers coming back from Brussels.
"I don't feel in any way let down by Mr Russell because Mr Russell was always clear with the UK Government that he wasn't the decision maker - that any decision on agreements that he discussed with us would have to be cleared by First Minister Nicola Sturgeon.
"He made that very clear - so we didn't think we'd reached an agreement with the Scottish Government, we know that if an agreement had been discussed, then Michael Russell would have to bring that back to the First Minister."