Nicola Sturgeon has branded Brexit a "reckless gamble" as she said Scotland should be allowed to choose its own future once the terms of the UK's departure from the European Union are clear.

Theresa May's triggering of Article 50, formally starting the EU exit process, is a "leap in the dark", the First Minister added.

She was speaking after SNP Westminster leader Angus Robertson warned the Prime Minister that denying Scots a vote between Brexit and independence will make the break-up of the UK "inevitable".

Mrs May, however, argued Brexit would make the country "more united", adding that Holyrood and the other devolved governments should expect a "significant increase" in powers as a result of the change.

In the Article 50 letter, which has now been delivered to European Council President Donald Tusk, Mrs May stressed that in the Brexit talks "we will negotiate as one United Kingdom".

She added "the specific interests of every nation and region of the UK" would be taken into consideration during the process.

But the First Minister said: "Fully nine months after the EU referendum, the UK Government still cannot answer basic questions about what Brexit will mean for businesses, for the economy generally, and for the type of society we live in.

"I wish the Prime Minister well in the negotiations which lie ahead, because a good Brexit deal for the UK is in Scotland's interests.

"But the UK Government's hard-line approach to Brexit is a reckless gamble, and it is clear, even at these very early stages, that the final deal is almost certain to be worse economically than the existing arrangements - and potentially much worse.

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"Scotland voted decisively to remain part of Europe, but the UK Government only formally responded with a dismissal of our compromise proposals to keep Scotland in the single market at the same time as the Article 50 letter was sent.

"The next two years are hugely important and will determine the kind of country Scotland will become.

"The Prime Minister has today confirmed her aim is to reach a Brexit agreement covering a future relationship within two years. So the people of Scotland must have the final say on their own future once the terms of Brexit are clear."

On Tuesday, MSPs at Holyrood voted by 69 to 59 in favour of a second Scottish independence referendum.

Mr Robertson highlighted the result as he warned the Prime Minister that "if she remains intransigent, and if she denies Scotland a choice on our future, she will make Scottish independence inevitable".

He also accused the Prime Minister of having "broken her word" after she promised an agreement would be put in place with the devolved administrations before Brexit was triggered.

Amid noisy exchanges in the Commons, the SNP MP said his party had become accustomed to "members on the other side of the house being incapable of understanding that the people of Scotland voted to remain in the European Union".

But Mrs May told him: "The point is that we are one United Kingdom and it was a vote of the whole United Kingdom."

She insisted that in the wake of the ballot, most people want politicians to "respect that vote and get on with the job of delivering for everybody across the whole of the United Kingdom".

Mr Robertson hit back: "The United Kingdom is a multinational state, with four nations - and two of them voted to stay and two voted to leave, and all of the rhetoric from the Government benches does not paper over the gaping chasm that there is not unity in this so-called United Kingdom."

The SNP also pointed to the draft European Parliament resolution, which will form the basis of the first official response to the triggering of Article 50.

The resolution, which will be adopted next week in Strasbourg, states that in the referendum in 2016 a "large number of United Kingdom citizens, including a majority in Northern Ireland and Scotland, voted to remain in the European Union".