BORIS Johnson’s cast-iron pledge to refuse a second independence referendum will have a shelf life of a matter of months if he wins the election, Nicola Sturgeon has said.

The First Minister also insisted a hung parliament on December 12 – in which no party gains overall control – would be the best outcome for Scotland because it hands the SNP influence and power.

Ms Sturgeon made the comments as she launched the SNP’s general election campaign in Edinburgh, in the shadow of the Scottish Parliament.

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The event came a day after Mr Johnson ruled out ever agreeing to another referendum during a fleeting visit to Scotland – even if the SNP wins a majority at the next Holyrood election in 2021.

Speaking to candidates in the visitor attraction Dynamic Earth, Ms Sturgeon lambasted this position, insisting the SNP “already has a cast-iron mandate for an independence referendum, based on our explicit manifesto pledge for the 2016 Holyrood election”.

Elsewhere, she outlined her demands if Jeremy Corbyn seeks her party’s support to secure the keys to Downing Street – including a referendum, social security reform and further devolution.

She said: “Nothing Boris Johnson has said in his short time as Prime Minister has turned out to be the case, so perhaps that should give us all hope for the future.

“Firstly, if you listen to Boris Johnson’s comments, what he appears to be saying to Scotland, pretty much in terms, is, ‘I don’t care how Scotland votes – however you vote, I’m going to ignore you’.

“I would say to the people of Scotland – this election is a great opportunity for us to show Boris Johnson exactly what we think of such a contemptuous and disrespectful attitude towards Scottish democracy.

“But secondly, the position Boris Johnson articulated yesterday is not a sensible, serious or sustainable position – that he will block Scottish democracy forever and a day.

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“And I will predict confidently at this podium here today, that that position that he articulated yesterday will turn out to have a shelf life only about as long as his, ‘We will leave the European Union on October 31, do or die, or I’ll be dead in a ditch somewhere otherwise’.

“This is not a man whose word from day to day can be taken seriously.

“But more fundamentally, the power of public opinion in Scotland will see that position proven to be unsustainable.

“We already see it crumbling before our eyes in the Labour Party, and I don’t think it will be long before we see it happening elsewhere.”

Ms Sturgeon insisted a vote for the SNP is a vote to escape Brexit, and launched a broadside at the pro-EU Liberal Democrats.

She said: “And for the Liberal Democrats, despite all their talk, maintaining Westminster control over Scotland, even under Boris Johnson, is more important to them than maintaining Scotland’s place in Europe.

“When it comes down to it the Liberal Democrats in Scotland are not the party of remain.

“They are just another party of Westminster. They would rather subject Scotland to a Tory Brexit than give people in Scotland a choice over our future.”

She later added: “If you want, in Scotland, to vote for a party that is unambiguously for Scotland’s membership of the EU, that wants to see the UK remain in the EU, than I would argue – in my entirely unbiased opinion – that voting SNP is the best way to achieve that.”

The First Minister said there are no circumstances in which her party would support a Boris Johnson government.

And she argued a hung parliament is “in many ways potentially the best outcome for Scotland, because it gives us significant influence and power in that scenario”.

Ms Sturgeon made clear the price of SNP support for a minority Labour government would be a second referendum next year, but also listed issues such as an end to austerity, social security reform, further devolution and greater action on climate change.

She said: “I would never support a Conservative government. I can’t foresee the SNP being in a formal coalition, but we would look, as I’ve said in the previous two general elections, to form alliances to keep the Tories out of power.

“As I’ve said today, we would drive a hard bargain. There would be significant issues that we would want to advance for any support from the SNP.

“Any party – if that’s Labour after the election – that finds itself in a minority situation needs the support of other parties.”

She added: “That position gives Scotland significant influence. But the first step we’ve got to take to make sure we can get there is vote in a way in Scotland that helps deprive Boris Johnson of the majority he wants and put the SNP into the driving seat.”

Labour has ruled out any pacts or deals with the SNP, insisting it would simply put its agenda before Parliament as a minority government and dare the SNP to vote it down.

But Ms Sturgeon said the “reality” is that any minority Labour administration would need the support of the SNP.

She added: “That’s the reality of the situation, and it gives the SNP and by extension – given that we are there to represent Scotland’s interests – Scotland significant influence and significant power, which is why the more SNP MPs there are after this election, the more influence we will have.”