Tony Blair will urge opponents of Brexit to fight to change people’s minds and reverse Britain’s decision to leave the European Union, in a speech that aims to show U.K. Prime Minister Theresa May that she won’t get everything her own way.

“People voted without knowledge of the true terms of Brexit,” the former Labour premier will say in a speech in London on Friday, according to extracts e-mailed by the pro-EU campaign group Open Britain. “As these terms become clear, it is their right to change their mind. Our mission is to persuade them to do so.”

Blair, who ran the country from 1997 to 2007, will explicitly set himself against May’s Conservative government, which he’ll accuse of being a “government for Brexit, of Brexit and dominated by Brexit.” As the most formidable election-winner in Labour’s history, his intervention isn’t to be dismissed, but opponents are likely to argue that his campaigning strength is diminished by his support for the Iraq War.

Blair will set out his stall in a speech at Bloomberg LP’s European headquarters in London, the same place where, in January 2013, former Prime Minister David Cameron announced his plan to call a referendum on EU membership, unwittingly setting Britain on course to leave.

Now May is steering the U.K. toward a so-called hard Brexit, saying she wants to withdraw not just from the 28-nation EU, but also its single market and customs union, both of which can accommodate countries that aren’t in the bloc. That’s riled opponents of Brexit, who argue that it ignores the wishes of the 48 percent of voters who opted for Remain in last year’s referendum.

‘Brexit At any Cost’

“Those driving this always wanted a hard Brexit,” Blair will argue. “Indeed even the term hard Brexit requires amendment. The policy is now Brexit at any cost.”

Read more: A Q&A explainer on May’s vision for Brexit

With the Labour Party now deeply divided and unsure of how to respond to the Brexit vote, the government has had a relatively easy ride from Brexit opponents in parliament. Last week May won a series of votes on the legislation to allow her to begin departure talks, which she aims to trigger by the end of March. Blair’s aim is to rally those who want to stay inside the EU and get them to work together to change the terms of the debate.

“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,” Blair is due to say. “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 explicitly reject May’s argument that her opponents are “citizens of nowhere.”

“How hideously, in this debate, is the mantle of patriotism abused,” Blair will say. “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.”

Blair will agree with May that support for Brexit is driven by immigration, but he’ll argue that leaving the EU won’t deal with the immigration that concerns people.

“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,” he’ll say. Nevertheless, the debate has changed in just a few months “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.”