Tony Blair is set to provoke a furious political row by calling on opponents of Brexit to "rise up" and persuade voters to change their mind about leaving the EU.
In a rallying cry to pro-EU MPs and peers, the former PM will accuse Theresa May of pursuing Brexit at any cost and warn it could lead to Scottish independence.
Mr Blair, who wants a second referendum and has pledged to campaign to keep the UK in the EU, will deliver his latest attack on Brexit in a powerful speech to Remain supporters.
His speech will also be seen as a signal that he would like to create a new pro-Remain political party made up of Blairites, Liberal Democrats and even some pro-EU Conservatives.
But Mr Blair will face a bitter backlash from leading Brexit supporters and puts himself at odds with Jeremy Corbyn, who last week ordered Labour MPs to vote for the Government’s Article 50 bill.
Speaking only days before the bill is debated in the House of Lords, Mr Blair will say: This is not the time for retreat, indifference or despair; but the time to rise up in defence of what we believe.
The Brexit Secretary David Davis admitted this week that the Government is expecting amendments to be passed by peers and predicted ping pong between the Commons and the Lords.
Mr Blair is making his speech to the Open Britain group, whose leading figures include Lib Dems Nick Clegg and Norman Lamb, Labour’s Chuka Umunna and Pat McFadden, and Tories Anna Soubry and Dominic Grieve.
Acknowledging that the will of the people should prevail, he will say: 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 will say: This is a Government for Brexit, of Brexit and dominated by Brexit. It is a mono-purpose political entity.
Those driving this always wanted a hard Brexit. Indeed, even the term hard Brexit requires amendment. The policy is now ‘Brexit at any cost’.
Our challenge is to expose relentlessly the actual cost, to show how this decision was based on imperfect knowledge which will now become informed knowledge; to calculate in easy to understand ways how proceeding will cause real damage to the country and its citizens, and to build support for finding a way out from the present rush over the cliff’s edge.
I don’t know if we can succeed, but I do know we will suffer a rancorous verdict from future generations if we do not try.
He will add: How hideously, in this debate, is the mantle of patriotism abused.
We do not argue for Britain in Europe because we are citizens of nowhere.
We argue for it precisely because we are proud citizens of our country who believe that in the 21st century, we should maintain our partnership with the biggest political union and largest commercial market right on our doorstep; not in diminution of our national interest, but in satisfaction of it.
Declaring that immigration is driving the Brexit debate, Mr Blair will say: There is in some parts of the country a genuine concern about numbers from Europe – real pressures on services and wages.
But for many people, the core of the immigration question – and one which I fully accept is a substantial issue – is immigration from non-European countries, especially when from different cultures in which assimilation and potential security threats can be an issue.
Nonetheless, we have moved in a few months from a debate about what sort of Brexit, involving a balanced consideration of all the different possibilities, to the primacy of one consideration – namely controlling immigration from the EU – without any real discussion as to why and when Brexit doesn’t affect the immigration people most care about.
Mr Blair will also warn of the break up of the UK.
In addition to all this, the possibility of the break up of the UK – narrowly avoided by the result of the Scottish referendum – is now back on the table, but this time with a context much more credible for the independence case.
We are already seeing the destabilising impact of worry over border arrangements on the Northern Ireland peace process.
(c) Sky News 2017: Tony Blair to tell Brexit critics: It’s ‘time to rise up’