THERESA May has been warned ministers risk “stumbling into the next phase of negotiations with the EU without a plan” putting the UK at a disadvantage in the “tougher” second stage of Brexit.

The warning comes in a highly critical report by the Institute for Government think tank which also recommends the Government should involve the devolved nations early and consistently in the process.

It gives a damning assessment of how the Government handled the first phase of the Brexit process saying the UK Government’s approach "was bedevilled by the absence of Cabinet agreement” and that “politicians, particularly on the Government backbenches, did not trust the UK’s official negotiators”.

It added: “The Government engaged Parliament late, alienated the devolved governments and failed to make use of external expertise”.

The authors warn talks to hammer out a final deal to determine ongoing relations between the UK and the EU are expected to be tougher than the divorce phase of the talks which ended last year with May’s withdrawal agreement – now the subject of a Commons deadlock.

Published today – Negotiating Brexit: Preparing for talks on the UK’s future relationship with the EU – it recommends before negotiations on the future relationship begin, the Government should publish its ambition for the way ahead without drawing red lines.

It recommends that: “The PM appoints a ministerial deputy, based in the Cabinet Office, to oversee the day-to-day negotiations (taking that role away from DExEU).

“The Government finds a way to use the expertise in the Department for International Trade (DIT) whose staff currently have little role in the EU negotiations.

"The Government should engage Parliament and the devolved administrations early and consistently."

Brexit Secretary Michael Russell said: “This report merely confirms what we have... said – Scotland has been ignored by the UK Government throughout the Brexit process with scant, if any, notice taken of our overwhelming vote to remain in the EU. The Scottish Government’s detailed compromise proposals have also been ignored or dismissed at every turn.”