London Some saw it as using Brexit to return to frontline politics, others said it was a year too late, but sharp divisions over Britain’s decision to exit the EU have resurfaced as former prime minister Tony Blair launched a “mission” on Friday to reverse the leave vote.Calling for people to “rise up” against Brexit and to try to change people’s minds about its adverse impact on the British economy and other spheres, Blair accused the British news media of being largely pro-Brexit.Blair said in a speech at an event organised by the pro-European campaign group Open Britain that those seeking to leave the EU always wanted a hard Brexit, which means leaving the European Single Market and the jurisdiction of the European Court of Justice, among other key links.Indeed even the term 'Hard Brexit' requires amendment. The policy is now 'Brexit at any cost'. Our challenge is to expose, relentlessly, what that cost is. To show how this decision was based on imperfect knowledge, which will now become informed knowledge,” he said.Blair regretted that his Labour Party was in a “debilitating” state but called for his campaign to cross parties and rally those who wanted to remain in the EU. He said he accepted the verdict of last year’s referendum, but would recommend looking again at Brexit when we have a clear sense of where we're going. On leaving the EU, he said: The pain is large and the gain is largely illusory. The ideologues are the ones who are driving the bus.” He stressed that the Theresa May government has bandwidth for only one thing — Brexit, at the cost of other concerns,This is a government for Brexit, of Brexit and dominated by Brexit . It's a mono-purpose political entity and nothing else therefore truly matters, he said.However, with the cloud of the Iraq war hanging over his head, Blair’s point that the Brexit vote was based on “imperfect knowledge” was immediately ridiculed by many, who pointed out his decision to take Britain to war in Iraq too was based on “imperfect knowledge”.Senior Conservative leader Iain Duncan Smith called Blair arrogant and his intervention “nonsense”, while Downing Street insisted the government was absolutely committed to deliver Brexit as decided in the June 23, 2016 referendum.Blair was also reminded it was under his government that Britain allowed unfettered migration from EU countries — one of the key concerns that led to the 52% vote to leave the EU.