British Prime Minister Theresa May is preparing to reject a demand by Nicola Sturgeon for a second Scottish referendum, reports say.

The Scottish First Minister said on Monday she will seek Holyrood's approval next week for a new vote on Scottish independence.

But The Times in Britain reports Mrs May will refuse to allow the vote to take place in the next two years.

Ms Sturgeon has said the so-called indyref2 should be held between autumn 2018 and spring 2019.

Making the announcement in Edinburgh, the SNP leader said she believed people would now choose to break away from the UK in order to stay in the EU.

In 2014, Scotland voted to stay part of the UK by 55.3% to 44.7%; but in the Brexit vote, Scots voted to remain in the EU by 62% to 38%.

Ms Sturgeon said it was about protecting Scotland's interests in "circumstances we didn't ask to be in".

She said Scotland was now at a "hugely important crossroads".

Mrs May accused the SNP of "tunnel vision" and insisted she wants to negotiate a Brexit deal "for the whole of the United Kingdom".

Ms Sturgeon said the proposed timing of the referendum would mean the terms of Brexit would likely be known and therefore voters could make an informed decision.

MSPs at the Holyrood parliament, where there is a pro-independence majority, must first back her call.

The proposal will then move to Westminster, where MPs and the Lords must also support the proposal.

"Tunnel vision"

Polls since the Brexit vote have shown that support for Scottish independence has been relatively unchanged since the first referendum in 2014.

But last week an Ipsos-Mori poll found that 50% of those north of the border backed separation.

Ms Sturgeon announced her plans hours before the House of Lords decided not to try to amend the Brexit bill, which left Mrs May free to trigger Article 50 at a time of her choosing.

"The Scottish Government's mandate for offering this choice is beyond doubt," said Ms Sturgeon.

"So next week I will seek the approval of the Scottish Parliament to open discussions with the UK government on the details of a Section 30 order - the procedure that will enable the Scottish Parliament to legislate for an independence referendum."

Mrs May was quick to react to Ms Sturgeon's announcement, hitting back at her claim that the government had put up a "brick wall" over Brexit arrangements.

"We've been working closely with the devolved administrations," Mes May said.

"We've been listening to their proposals; and recognising the many areas of common ground we have, such as protecting workers' rights and our security from crime and terrorism."

Mrs May added: "The tunnel vision that the SNP has shown today is deeply regrettable. It sets Scotland on a course for more uncertainty and division," she said.

"This is at a time when the evidence is that the majority of the Scottish people do not want a second independence referendum.

"Instead of playing politics with the future of our country, the Scottish government should focus on delivering good government and public services for the people of Scotland - politics is not a game."

The Times said some had speculated that Mrs May could leave the door open to a second independence vote but only if the SNP wins an absolute majority in the next Holyrood elections in 2021.