Britain's former Prime Minister and former Labour Party leader, Tony Blair, speaks at an event attended by Labour supporters in central London on July 2015 | Justin Tallis/AFP via Getty Images Tony Blair joins fight against Brexit — and Jeremy Corbyn Former Labour prime minister says Leave campaigners want to erode social protections provided by the EU.

LONDON — Tony Blair intervened in the Brexit debate Tuesday to warn Labour voters not to believe the “unholy alliance” of left-wingers and free-market Conservatives who want to pull the U.K. out of the European Union.

The former prime minister, who flew into the U.K. overnight, said the campaign to leave the EU was a “two-step dance” to erode social protections and set up an ultra-free market economy. His remarks come amid criticism that Labour leader Jeremy Corbyn — a life-long Euroskeptic — has not been outspoken enough in his support for the Remain campaign.

Speaking at a question-and-answer session in central London, Blair lambasted the hard-left’s “take over” of the Labour Party under Corbyn, suggested he had little chance of winning in 2020, and made an impassioned plea for centrist politicians across Europe to do better.

Blair also backed Conservative Prime Minister David Cameron's criticism of Donald Trump’s proposed ban on Muslims entering the U.S., and warned that the fight against Islamist terror would be more like the Cold War in its scale and breadth.

Intervening for the first time in the EU referendum campaign, Blair said working-class Labour voters would be “really, really important in establishing a majority to stay in the European Union” and needed to be mobilized.

“On the Leave side is a really unholy alliance of people, some of whom are protectionist, but many of whom are advocating Europe as a two-step dance," he said. "The first is to get out of Europe, but what they are really anxious about is some of the social protections.”

Isolationists

Blair praised the Remain campaign for running a “pretty strong, effective campaign, focusing on the right issues” and revealed that he would get involved in the next few weeks. “There’s a role for former prime ministers,” he said.

There was a “big opportunity” for the U.K. in Europe if the country votes to stay in because Cameron will be able to tell other European leaders that he has settled this issue within Britain, and present an opportunity to get the right type of relationship with Europe, said Blair.

Turning to the current Labour Party leadership, Blair suggested Corbyn was doomed to fail.

He said: “I thought I was pretty good at politics, but I look at politics today and I’m not sure I understand it.”

Blair said the center had lost its way across Europe, adding: “Let’s say it’s not yet a proven concept that Corbynism can win an election.”

The former prime minister said his party had been “taken over” by the hard left. “It’s clear they can take over a political party, but what’s less clear is if they can take over a country.”

He said both the hard left and hard right were similar. “They are both isolationist, they are both coming out very strongly about free trade. The left want to hang the bankers and the right want to kick out the immigrants. Why can’t the center bring itself back into proper contention?”

Speaking to Bronwen Maddox, editor of Prospect Magazine, Blair also defended his record on immigration.

Asked if it had been a mistake to grant freedom of movement rights to Eastern European countries he said: “Personally I don’t. I know that there is a criticism, that I understand, that we shouldn’t have allowed free movement of people earlier than we needed to from Eastern Europe.”

He said the U.K. should be “proud” of championing Eastern Europe’s accession into the EU, adding: “The people who have come into this country have contributed far more in taxes than they have taken out in taxes. The answers to Britain’s problem today is not to become anti-immigrant.”

Blair also dismissed claims from the Leave campaign that Turkish entry into the EU was on the cards. “This is a long, long time away. Britain, like every other country in Europe, has a veto. But this is not a realistic debate for this referendum.”