Scottish devolution "should be treated with respect" by the UK Government, which needs to "rethink" its constitutional arrangements in light of Brexit, a committee of MPs has said.

The report by Westminster's public administration and constitutional affairs committee urges UK ministers to establish a "clear devolution policy for the Union as we leave the EU".

It also recommends a root-and-branch review of how Whitehall works with the devolved governments, saying the abolition of the Scotland Office and the position of Scottish secretary, currently held by David Mundell, should be considered.

The devolution settlements were set up 20 years ago in the context of EU membership, said committee chairman Sir Bernard Jenkin, which "masked many key constitutional questions and ambiguities".

These questions and ambiguities will become "more pressing" as Britain leaves the EU, he added.

Sir Bernard said: "Leaving the EU will change the UK's constitutional arrangements, so it needs a rethink.

"We recommend the government sets out a clear devolution policy for the Union as we leave the EU.

"Failure to do this just prolongs misunderstandings which are the basis for more conflict."

The report adds: "Devolution is now an established and significant feature of the UK constitutional architecture and should be treated with respect to maintain the integrity of the United Kingdom."

The UK and Scottish administrations are currently entangled in a Supreme Court battle relating to accusations of a "power grab" over how 24 powers should be returned from Brussels after Brexit.

Sir Bernard said the "acrimony" with Welsh and Scottish administrations over the EU Withdrawal Bill was "highly regrettable" and "avoidable" with better consultation.

He called for a new system of inter-governmental relations to be set out in law, adding: "The present machinery for developing inter-governmental relations is flimsy, and there is nothing to give the various parts of England a say.

"Ignoring this risks the future relations within the UK.

"We set out a path to reconciling differences and building strong relationships across the UK, which recognises that many parts of England have more in common with parts of Scotland, Wales or Northern Ireland than they do with London and the South East."

The committee has suggested a new "devolution policy for the Union" should be issued at the start of every parliament.

It also says UK minister should conduct a "systematic review" in the year after Brexit "of how Whitehall is structured and how it relates to the devolved administrations in Scotland, Wales and Northern Ireland".

The report adds: "This review should also consider whether the role of the territorial offices in Whitehall and corresponding secretaries of State are still necessary and, if they are, whether they might be reformed to promote better relations across Whitehall with the devolved administrations."

The committee also acknowledges how political changes have "arguably qualified sovereignty within the UK" through the "introduction of popular sovereignty" in the devolution settlement and referendums.

This means, although the "ultimate supremacy" of the UK Parliament is legal fact, sovereignty as a political concept has "changed the balance of power".

SNP MP Ronnie Cowan, who sits on the committee, said the state of relationships between devolved administrations and the Government could explain why the UK is now facing "the utter chaos of a no-deal Brexit".

He said: "If the Tories had engaged with the devolved administrations after the Brexit referendum and had a grown-up conversation that allowed for input and constructive criticism, then we could be in a very different place.

"Instead the UK Government internalised all their rows and are completely bogged down in their own divisions.

"If this is the same management style that has been adopted while engaging with the EU 27 then it's no wonder the negotiations are in the shambolic state that they are."

Labour's shadow Scottish secretary Lesley Laird said: "This damning report should be a wake up call for the UK Government.

"It confirms what we already knew - that the devolved administrations have been treated disrespectfully and disgracefully and have had nowhere near enough say over Brexit negotiations and how it affects them.

"Essentially this report makes clear that the current constitutional structures of this country are not working.

"Labour has continually called for reform to ensure devolved administrations do have a say and that there is far greater openness over what the UK Government says and does in relation to devolution."

She added: "I hope that the UK Government, and in particular David Mundell, will now take a long look in the mirror and reflect on the mess that they have managed to make of this situation."

A UK Government spokeswoman said: "We are committed to securing a deal that works for the entire United Kingdom and have been absolutely clear that when devolved powers are returned from Brussels, the vast majority will go straight to the devolved administrations.

"For the past year, we have been focused on constructively engaging with the devolved administrations and continue to have regular meetings with them, held at all levels, including the Joint Ministerial Committees and Ministerial Forums.

"All sides have committed to continuing to work together, including building common frameworks so that UK businesses won't face a cliff edge on the day we leave the EU."