A CROSS-PARTY summit should be held in an attempt to break the deadlock over the return of devolved powers after Brexit, Richard Leonard has said.

The Scottish Labour leader has written to Cabinet Office minister David Lidington and Scottish Brexit minister Mike Russell to propose last-ditch talks between the UK Government, Scottish Government and the parties that make up Holyrood.

It comes as tensions within Theresa May’s Cabinet continue to erupt, with Michael Gove insisting there are "significant question marks" over the customs partnership option favoured by the Prime Minister for post-Brexit trade.

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The Environment Secretary made the remarks after a plea by Mrs May for unity as she insisted she could be trusted to deliver the Brexit people voted for.

Mr Leonard’s call comes ahead of a crucial vote in the Scottish Parliament tomorrow, in which MSPs are expected to reject the Conservative Government’s flagship EU Withdrawal Bill.

Scottish ministers insist Clause 11 of the legislation – which deals with the return of devolved powers from Brussels after Brexit – represents a “power grab”, a position supported by all of Scotland’s parties except the Tories.

In his letter, Mr Leonard wrote: “It is clear that we are now in a very difficult phase in the discussions, in which it is necessary to build trust and confidence to secure a satisfactory outcome.

“In light of that I would like to propose that the most constructive confidence-building step at this stage would be cross-party talks involving the UK Government, the Scottish Government and representatives of parties in the Scottish Parliament.

“Talks on this basis would help us explore how we can achieve a consensus and so a breakthrough that delivers on the objective of protecting democracy and devolution.”

Mr Leonard’s position is at odds with the Labour-led Welsh Government, which had teamed up with the Scottish Government to refuse granting consent to the Brexit Bill but struck a deal with UK ministers last month.

However, UK Labour leader Jeremy Corbyn backed his party in Scotland last week, insisting “quite clearly there is a power grab going on by Whitehall”.

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Tomorrow’s vote is expected to pave the way for a major constitutional clash between Westminster and Holyrood, which could lead to UK ministers imposing Brexit legislation without the latter’s consent.

Meanwhile, Mrs May’s Cabinet is split over which of two post-Brexit customs models to back, with Mr Gove yesterday suggesting neither option was perfect.

Pressed on whether Foreign Secretary Boris Johnson was right to brand the customs partnership option as "crazy", he told the BBC: "Across Government, across Cabinet, there is agreement that neither of these two models is absolutely perfect.

"And with the new customs partnership, Boris pointed out that because it's novel, because no model like this exists, there have to be significant question marks over the deliverability of it on time."

Mrs May has set up two Cabinet groups to consider the customs options, but favours a system that would see the UK collecting tariffs on behalf of Brussels.

Shadow Brexit secretary Sir Keir Starmer branded the divisions within the Government a “farcical situation”.

Asked about Mr Leonard's letter, Mr Russell said the Scottish Government “continue to talk to all the parties at Holyrood on regular basis and are very open to ideas from them to try and resolve this impasse”.

He added: “I am happy to talk to Richard Leonard about any suggestions he has at any time and to ensure they are factored into our approach to the UK Government.

“The EU Withdrawal Bill in its current form would give the UK Government the power to prevent the Scottish Parliament from passing legislation in key areas such as farming, fishing and the environment for up to seven years.

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“That is not acceptable and there is cross-party support for the position that in its current form, the Scottish Parliament could not give legislative consent to the bill.”

A Cabinet Office spokeswoman said the UK and Welsh Government had reached an agreement that will see “comprehensive changes” to Clause 11, and insisted it was “disappointing” Scottish ministers had not signed up.

She added: “But we welcome any move towards constructive dialogue and want to be clear that the door is still open to them to do so.”