The British Prime Minister has confirmed receipt of a letter from the Scottish First Minister formally requesting a new independence referendum.

In the letter, Nicola Sturgeon insisted that there is “no rational reason” for Downing Street to block the vote.

The Scottish Parliament voted in favour of a new referendum on Tuesday, however Westminster must give its approval before the poll can be held.

The Scottish National Party (SNP) has insisted the new referendum is justified due to the significant implications of the UKs planned exit from the European Union.

In the Brexit referendum, Scotland voted to remain in the EU by a majority of 62%.

Northern Irish voters also opted to remain, however the Welsh and English vote to leave swung the referendum in favour of an exit for all four territories.

In the letter, Ms Sturgeon said that although the Brexit negotiations are yet to get underway, it seems inevitable the outcome will leave the UK outside the European single market.

"In these very changed circumstances, the people of Scotland must have the right to choose our own future - in short, to exercise our right of self-determination," Ms Sturgeon wrote in her letter to Downing Street.

Scotland is hoping to hold the vote between autumn 2018 and spring 2019 – however the British government is set to refuse permission.

British Prime Minister Theresa May has claimed that now is not the time for another vote, after Scottish voters rejected independence in 2014.

Ms Sturgeon on the other hand insists that the Brexit vote has dramatically altered the situation and pointed out that she was elected on a mandate that promised a new independence referendum should Brexit come to pass.

"It is my firm view that the mandate of the Scottish Parliament must be respected and progressed," she wrote. "The question is not if, but how."

"I hope that will be by constructive discussion between our governments.

"However, if that is not yet possible, I will set out to the Scottish Parliament the steps I intend to take to ensure that progress is made towards a referendum."

A spokesperson for Downing Street has confirmed that Mrs May received the letter.

He said that Westminster will respond in due course but ruled out discussions on second independence referendum.

"At this point, all our focus should be on our negotiations with the European Union, making sure we get the right deal for the whole of the UK," the spokesman said.

Ms Sturgeon has called for the referendum to take place after the final terms of the Brexit divorce are agreed.

"There appears to be no rational reason for you to stand in the way of the will of the Scottish Parliament and I hope you will not do so," she wrote.

Mrs May is aiming to reach a Brexit agreement with the EU by March 2019.