Image copyright PA Image caption Ms Leadsom formally launched her leadership campaign on Tuesday

A Conservative leadership candidate has said she would "never say never" to a second Scottish independence referendum if she becomes PM.

Andrea Leadsom said another referendum was not in the country's best interests and she does not want to see one.

But as a "big believer in devolution" it would be "disrespectful" for her to completely rule it out, she said.

First Minister Nicola Sturgeon wants to hold indyref2 within the next two years.

But she has indicated that she would need the agreement of the UK government before holding a referendum.

Downing Street had previously said it would not grant a new Section 30 order, which underpinned the 2014 referendum - a position that has been backed by many of the ten candidates to succeed Theresa May as prime minister.

But Ms Sturgeon has claimed that this position was "unsustainable" and has challenged her party to increase support and demand for independence.

Speaking at a lunch at Westminster on Tuesday, Ms Leadsom became the first candidate to publicly leave open the possibility of giving the Scottish Parliament the necessary consent to hold a referendum in the future.

Image copyright Getty Images Image caption Boris Johnson is the favourite to become prime minister - but is unpopular with the Scottish Conservative leadership

She said: "The reason I say 'never say never' is because I do not think that there should be another independence referendum in Scotland, I do not think it's in their interest, but on the other hand I am a big believer in devolution.

"So, what I just want to say is I am not going to stand here and utterly rule it out because I think that that is disrespectful.

"But I would very strongly fight against a second referendum, which I don't think is in the interest of Scotland and it's definitely not in the interests of the UK.

"What I think we have to be doing is promote the strength of the UK working together far stronger, far more than we have done and I have a number of policy areas that I would use to try and make that happen."

However, Ms Leadsom tweeted on Wednesday morning that "there will be no second referendums on my watch - not on Scottish independence and not on EU membership."

Her original comments could potentially be problematic for the Scottish Conservatives, who have pitched themselves as being staunch defenders of the union between Scotland and England.

John Lamont, the Conservative MP for Berwickshire, Roxburgh and Selkirk, tweeted that the party should be "standing up to Nicola Sturgeon's grandstanding, not giving in to SNP demands".

Scottish Labour MP Ian Murray claimed that Ms Leadsom's comments showed that the Conservatives "can't be trusted to protect Scotland's place in the Union".

However, Ian Blackford - the SNP's leader at Westminster - said Ms Leadsom "is right to recognise that it would be deeply disrespectful for Westminster to rule it out - it would be a democratic outrage for the Tories to stand in the way of democracy".

Separately, claims that fellow leadership candidate Boris Johnson would be unpopular in Scotland are "nonsense", according to a Scottish Tory MP who is backing him to become prime minister.

Ross Thomson insisted that the former foreign secretary could "unite us and make us believe in ourselves again".

But in an interview with BBC Scotland, Mr Thomson appeared to distance himself from Mr Johnson's plan to cut income tax for high earners and increase national insurance payments.

Some experts say it could see wealthier Scots pay up to £8,000 a year more than their counterparts elsewhere in the UK - but the Institute for Fiscal Studies (IFS) has argued that the Scottish government would actually see its budget increase under the plan.

Mr Johnson, who is widely seen as the favourite to win the contest, has been heavily criticised in the past by both Scottish Secretary David Mundell and Scottish Conservative leader Ruth Davidson - who announced at the weekend she was backing Sajid Javid in the contest.

Ms Sturgeon has repeatedly predicted Mr Johnson would be a "disaster" in Downing Street and would boost the case for Scottish independence.

What has Mr Thomson said about Mr Johnson?

Image caption Mr Thomson is an outspoken supporter of Brexit and a close ally of Mr Johnson

In a blog post on his personal website, Mr Thomson said Mr Johnson could "deliver for the people of Scotland and the whole United Kingdom" and hit out at the "twitterati and the chattering classes" for claiming he was unpopular in Scotland.

He said: "It's nonsense. The same people said the same thing when he ran for Mayor of London in 'a Labour city'.

"The same people told me Aberdeen South never would elect a gay MP and that the Conservative and Unionist Party in Scotland would never back a working-class lesbian.

"They were wrong. And their lazy opinions, based on nothing but their own biases and those of the Scottish political bubble, are wrong now on Boris."

He argued that Mr Johnson is "fair, tolerant, compassionate" and had proven that he knows how to govern well during "two very successful terms as London Mayor".

Mr Thomson is the second Scottish Conservative MP to publicly back Mr Johnson, with Colin Clark doing so at the weekend.

What about Mr Johnson's tax plans?

His key campaign pledge so far has been to raise the higher rate of income tax from £50,000 to £80,000 - which would not apply in Scotland as income tax rates and bands are devolved to the Scottish Parliament.

However the policy would be part-funded by increasing employee National Insurance Contributions (NIC), over which Holyrood has no control.

Critics argue that higher earners in Scotland would therefore be paying more in NIC than they do at present, but would not benefit from Mr Johnson's income tax cut unless the Scottish government matches his proposal.

Image copyright Getty Images Image caption Mr Johnson and Ms Leadsom are among the ten candidates in the leadership race

The Chartered Institute of Taxation has calculated that people in Scotland who earn more than £80,000 would pay £7,844 a year more in tax than someone on the same salary elsewhere in the UK. The gap is currently about £1,500.

Meanwhile, Scottish workers on more than £60,000 would pay as much as £3,644 more than their counterparts south of the border.

However, the IFS argued that Scotland's fiscal framework means the reduction in tax bills and revenues in the rest of the UK would translate into higher block grant funding for the Scottish government.

It said: "This would allow for higher spending on public services north of the border. Or for the Scottish government to cut its own taxes - perhaps matching Mr Johnson's proposed cut to income tax for high earners."

The IFS also said that national insurance would be a "sensible candidate" to be devolved to Edinburgh in the future.

SNP MSP Angela Constance earlier said that taxpayers in Scotland were facing the prospect of "paying for a tax cut for the likes of Boris Johnson and his cronies".

She added: "That would be entirely indefensible - and is only likely to see a further rise in support for independence, which would give Scotland full powers over tax."

However, Mr Thomson told BBC Scotland that "things are said in the heat of the campaign'' and he is convinced Mr Johnson would do nothing to adversely affect Scottish workers.