THE SNP leadership has seized on Tony Blair’s words that the case for Scottish independence is "much more credible" after the Brexit vote and that a second referendum is now “back on the agenda”.

Nicola Sturgeon, the First Minister, tweeted: "Not his biggest fan but there's a quality of analysis & argument in Blair's speech today that has been totally lacking from Labour to date."

In a keynote address in London for Open Britain, which campaigns against a so-called "hard Brexit" outside the European single market, the former Prime Minister called on pro-Europeans to "rise up" and persuade Leave voters to change their minds in the face of a Conservative Government bent on pursing "Brexit at any cost".

Read more: Tony Blair: Pro-Europeans must rise up and persuade country Brexit is wrong

Despite the 52 to 48 per cent vote last June for Britain to leave the European Union and with the triggering of Article 50 to begin the withdrawal process just weeks away, Mr Blair contended that exiting the 28-strong bloc was not inevitable and called on progressives to make it their "mission" to reverse the outcome of the June 23 poll.

While Tim Farron, the leader of the Liberal Democrats, insisted: "Tony Blair is right,” and said the challenge now was to “persuade people to change their mind,” key Leave figures denounced the former PM’s intervention.

Boris Johnson, the Foreign Secretary, who led the Out campaign, denounced Mr Blair’s “bare-faced effrontery” and what he believed was his contempt for British democracy.

He said: “I respectfully say to Tony Blair, those who call on the British people to rise up against Brexit, I urge the British people to rise up and turn off the TV next time Tony Blair comes on with his condescending campaign."

Former minister and Leave campaigner Dominic Raab pointed to new ICM polling which suggested 68 per cent of voters now wanted the Government to crack on with Brexit compared to just 54 per cent in December. "These figures show how out of touch Tony Blair is with the mood of the country. Far from wanting to reverse the referendum, the overwhelming majority want the result respected and for politicians to get on with making a success of Brexit," he said.

Read more: Tony Blair: Pro-Europeans must rise up and persuade country Brexit is wrong

But the ex-PM also raised the constitutional debate on Scotland's future and argued that the Brexit vote had re-energised the issue of independence.

He said: "In addition to all this, there is the possibility of the break-up of the UK, narrowly avoided by the result of the Scottish referendum, but now back on the table; but this time with a context much more credible for the independence case."

Questioned following the speech, he stressed how he wanted Scotland to remain in the UK even if Brexit went ahead, noting how Scotland's single market with England was of “far greater importance to it economically than Scotland's interaction with the rest of Europe”.

But he added: "When myself and John Major warned this[Brexit] would be a threat to the UK we meant it and it was true; you can see that by the referendum coming back on the agenda."

Stephen Gethins for the SNP seized on the remarks, saying: ''The case for independence is more compelling than ever and will only become even more so when the full impact of a Tory hard Brexit with its economic and other consequences starts to become clear.

"Tony Blair's comments simply reflect the reality that the independence debate now is fundamentally different to the one in 2014 and the Tories' threat of a hard Brexit at any cost to Scotland is only going to see support for an independent Scotland rise further still.”

The party’s Europe spokesman added: “We are determined to keep Scotland's place in the European single market - which is around eight times bigger than the UK's alone - and independence must be an option if it becomes clear, it is the best or only way of doing so."

Read more: Tony Blair: Pro-Europeans must rise up and persuade country Brexit is wrong

Ross Greer MSP, the Scottish Greens' external affairs spokesman, declared: "The case for independence is stronger now as it has ever been. Independence would allow Scotland to stay with Europe and avoid the angry, isolated Brexit Britain planned by the Tories, one which will cost Scotland 80,000 jobs, a £2,000 drop in average wages and worse."

But Willie Rennie, the leader of the Scottish Liberal Democrat, argued that while Mr Blair was right about Europe, he was wrong about Scottish independence.

"The Conservatives' hard Brexit is bad for Britain's economy, which is why the public need the final say on the deal. But Tony Blair is wrong about independence. The case for independence is weaker, not stronger, now, especially with the £15 billion black hole in the Scottish public finances that would hit our NHS and schools," he added.

John Lamont, the Scottish Conservative chief whip, was also critical of the former PM. He said: "Tony Blair may not be aware of it but the fact is that only around a quarter of people in Scotland want another referendum on independence now."

Mr Lamont added that the SNP's attempts to use Brexit to muster support for another Scottish independence referendum had "failed".

Ian Murray for Scottish Labour Westminster said Mr Blair was right to highlight the “utter mess” the Tories were making of Brexit, noting how people did not vote to make themselves poorer but that was what would happen if Theresa May got her way.

"The Tory Brexit chaos has certainly given the SNP the excuse it was looking for to stoke up more grievance but the reality is that the economic case for separation is even worse now than when the people of Scotland rejected it in 2014,” argued the Edinburgh MP.

"On jobs, public finances, currency, trade, investment in schools and hospitals, and much more, Scotland benefits from remaining part of the UK. As Tony Blair said, the UK single market is our most important market.”

Read more: Tony Blair: Pro-Europeans must rise up and persuade country Brexit is wrong

The Scottish Labour MP added: "Labour will not support any SNP plan for another independence referendum. It's time the Nationalists focused on the day job of fixing the mess they have made of Scotland's schools and getting a grip of the crisis in our NHS."

In his speech, Mr Blair argued that when people voted last year they did not understood the full cost of withdrawal.

"I accept right now there is no widespread appetite to re-think but the people voted without knowledge of the true terms of Brexit. As these terms become clear, it is their right to change their mind. Our mission is to persuade them to do so,” he declared.

The former premier admitted he did not know if such a campaign would succeed but noted how “we will suffer a rancorous verdict from future generations if we do not try”.

He went on: "This is not the time for retreat, indifference or despair but the time to rise up in defence of what we believe; calmly, patiently, winning the argument by the force of argument but without fear and with the conviction we act in the true interests of Britain."

Read more: Tony Blair: Pro-Europeans must rise up and persuade country Brexit is wrong

Mr Blair also took a sideways swipe at the leadership of Jeremy Corbyn, saying that in the absence of any effective opposition, the pro-Europeans would have to form a cross-party movement to build support for Britain staying in the EU.

"The debilitation of the Labour Party is the facilitator of Brexit. I hate to say that but it is true. What this means is that we have to build a movement which stretches across party lines and devise new ways of communication," he added.

A Labour source responded: "No wonder we are still trying to recover from Tony Blair's legacy when he has such contempt for democracy.

"What he doesn't seem to realise is people voted Leave precisely because they felt let down by 13 years of the Davos Leftism he is still trying to flog."