Nicola Sturgeon has called on the Prime Minister to "apologise for the chaos he and his party have subjected" Scotland to for years.

Boris Johnson is urging Scots to use next month's "crucial" General Election to call a halt to the First Minister's plans for a second independence referendum.

The Prime Minister, who is campaigning in Scotland on Thursday, will urge voters north of the border to back the Conservatives - warning the only alternative is a Labour government under Jeremy Corbyn which would "spend next year dancing to the SNP's tune".

Ms Sturgeon, the SNP leader and Scottish First Minister, has already set out plans to hold a fresh vote on independence in the second half of 2020.

And with Labour pledging to hold another Brexit referendum if Mr Corbyn is voted into Downing Street, the PM warned against the prospect of having two "divisive" referendums next year.

Speaking ahead of his visit north, Mr Johnson said: "This is a crucial election for Scotland.

"A vote for the Scottish Conservatives is a vote to stop a second independence referendum and to get Brexit done so we can spend 2020 taking back control of our fishing waters, getting a fairer deal for our farmers, and investing in public services to give people better healthcare and better education.

"The other choice is a vote for Jeremy Corbyn who would spend next year dancing to the SNP's tune, wasting the year with two divisive referendums - one on the EU and one to give up on our union.

"Only a vote for the Conservatives will stop the SNP's plans to break up the UK - the most fantastic and successful political union in the world. I will never give up on our incredible union."

But Ms Sturgeon said: "The only thing Boris Johnson should be coming to Scotland to do is apologise for the chaos he and his party have subjected us to for years.

"He is a prime architect of the Brexit vote and the utter shambles it has now led to.

"A vote for the SNP is a vote to escape Brexit and to put Scotland's future in Scotland's hands - not Boris Johnson's."

She said her party is the main challenger to the Conservatives in the 13 seats they hold in Scotland - and added the SNP would "do our bit in trying to ensure his time in Downing Street has already come to an end".

The First Minister demanded: "Boris Johnson should apologise not just for the Brexit mess he has created, but also for a decade of Tory austerity that has caused so much misery for so many.

"He should also come clean on his Brexit deal and his plans for a no-deal exit in barely over a year's time if a trade deal cannot be agreed.

"That would be a disaster for Scotland and the rest of the UK, and it underlines the huge threat the Tories pose.

"Whatever happens in this election, Brexit will not in any sense be done - even if a deal is ultimately passed.

"It is an issue which is set to dominate Westminster politics, one way or another, for many years to come. That is why it is vital Scotland chooses to escape Brexit by opting for a better future with independence."

Ms Sturgeon has already said that if the SNP wins the most seats in Scotland on December 12, demands for a second ballot on leaving the UK will become "irresistible".

However, Richard Leonard has said he does not believe the SNP has a mandate for another Scottish independence referendum.

Speaking at his party's General Election campaign launch in the Maryhill area of Glasgow on Wednesday, the Scottish Labour leader said a decision on whether there is a mandate for another vote would need to be determined on the basis of future elections.

He added that he does not think the party would have a mandate even after the 2021 Holyrood election.

He said: "I don't know how you can predict an election in two years' time when one of the things which we are going to have to navigate is Brexit.

"The election of a Labour government in December will mean that by the middle of next year, the people will have a choice in a Brexit referendum.

"The premise currently of the SNP's call for a second independence referendum is Brexit.

"In six months' time, seven months' time, we could have a Remain vote in a Brexit poll of the people, which will take away that argument completely."

Mr Leonard also ruled out the prospect of any deals being struck between his party and the SNP in the event of a hung Parliament at Westminster.

He said: "There's no pact with the SNP, there will be no deals with the SNP, there will be no coalition with the SNP.

"But we've said that we are standing in this election to form a majority Labour government.

"If we were a minority Labour government, we would draft a Queens's Speech and it would then be up to the SNP whether they voted for that progressive, transformative Queen's Speech or not.

"And if they did not vote for it, they would have to answer to the people of Scotland why they did not vote for it."

Liberal Democrats are promising Scots a "brighter future" by halting both Brexit and SNP demands for a second independence vote.

Scottish Lib Dem leader Willie Rennie will highlight the party's opposition to both of these as he launches their election campaign.

With UK leader Jo Swinson insistent that she is a candidate to be the next prime minister, Mr Rennie said his party is "on the rise".

He will be joined by some of the Scottish Liberal Democrat candidates for next month's General Election for Thursday's launch event in Edinburgh.

Speaking ahead of that, he said: "Scottish Liberal Democrat candidates will fight to stop Brexit, stop independence and build a brighter future.

"We have a plan for the future which will invest in public services and tackle inequality.

"From the Shetland by-election to the European elections, the Liberal Democrats are on the rise, with a dynamic new leader in Jo Swinson."