First Minister Nicola Sturgeon has written to Prime Minister Theresa May to raise her concerns over the role of the devolved administrations during the Brexit talks.

In a letter sent on Monday, Ms Sturgeon called on the Prime Minister to provide greater clarity and assurances following reports of her strategy in trying to win a majority to pass her Brexit deal in Parliament.

Mrs May's deal has already been voted down twice by MPs.

Yesterday, John Bercow scuppered the chance of another Commons vote on the Prime Minister's deal before Thursday's EU summit, leading one minister to warn that the Government faces a "major constitutional crisis".

The First Minister described reports of a possible offer to the DUP in order to gain support for her deal as "concerning" and said that Scotland had been repeatedly ignored throughout the Brexit process.

She wrote: "As you are aware, like Northern Ireland, Scotland voted to remain in the European Union.

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"In the past two years however, Scotland's wishes and national interests have been roundly ignored and at times treated with contempt by the UK Government."

The First Minister highlighted her concern over the involvement the devolved nations could have in discussions over any future trade relationship between the UK and the EU.

She wrote: "Firstly, there must be no question of one political party - the DUP - being represented in talks on the future trade relationship between the UK and EU when other political parties and devolved governments are not.

"As you are aware, in August 2018, the Scottish Government published a paper in respect of our role in international trade negotiations.

"There has been no indication that the UK Government is taking these proposals seriously, although there has since been support for a greater role for devolved administrations in trade negotiations from both the International Trade and Scottish Affairs select Committees in the House of Commons.

"In addition, there have been no meaningful moves to ensure the devolved governments have a properly enhanced role in the next phase of EU-UK negotiations.

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"Secondly, the UK Government's proposals to the DUP appear to involve a serious curtailment of the powers of the Scottish Parliament.

"Many of the relevant rules fall within devolved competence and therefore it is not in the gift of the UK Government to unilaterally constrain the powers of the Scottish Parliament in order to strike a deal with the DUP.

"Continued alignment can only be guaranteed with the full support of the Scottish Government and Parliament.

"As you will be aware, the Scottish Government continues to be concerned that Scotland will be placed at a disadvantage if your proposals take effect."

Ms Sturgeon also said that funding to Northern Ireland (£1 billion as part of a confidence and supply agreement in 2017 and an additional allocation of £140 million in Northern Ireland's 2019-20 Budget) had served to short-change Scotland.

"The UK Government cannot continue to favour Northern Ireland over the other devolved administrations for short-term political gain and we expect any future funding to be allocated in a fair and transparent manner."

The First Minister also reiterated her support for holding another vote on leaving the EU.

She added: "I have said and will continue to say that while there is no broad consensus in the UK Parliament for your Brexit deal, the decision ought to be put back to the people in a second EU referendum - that is the responsible and democratic thing to do."

A UK Government spokesman said: "The Prime Minister is committed to delivering a Brexit that works for all parts of the United Kingdom - Scotland, Wales, England and Northern Ireland.

"The deal she has negotiated is in the best interests of businesses and households across Scotland and will bring new opportunities to fishing and farming communities.

"We have worked constructively with the Scottish Government throughout the Brexit process, consistently updating them on negotiations and listening to their views."