Blair is set to urge voters to speak out against the government's drive to exit the EU at any cost, saying it could damage future generations. He argues last year's vote to leave was "based on imperfect knowledge."
In excerpts of a speech he will give Friday, Blair says "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."
Blair is arguing that those who want to remain part of the single market are not unpatriotic. "We argue for it precisely because we are proud citizens of our country."