LONDON, April 7 — Tony Blair will weigh in behind Labour leader Ed Miliband, saying David Cameron’s promise to hold a referendum on Britain leaving the European Union risks economic insecurity.

The former Labour prime minister, who has previously expressed doubts about Miliband, will turn the Conservative slogan of “competence versus chaos” back on Cameron’s party.

“Think of the chaos produced by the possibility never mind the reality of Britain quitting Europe,” he’ll say in a speech in northern England today, according to extracts released by Labour. “Jobs that are secure suddenly insecure; investment decisions postponed or cancelled; a pall of unpredictability hanging over the British economy.”

Labour sees opposing the Tory promise of a referendum by 2017 as one of its strongest economic appeals. It was the focus of the party’s business manifesto, published last month. The parties are running neck-and-neck in the polls with the election a month away and neither set to gain a parliamentary majority.

Blair will say that it is “greatly to Ed Miliband’s credit” that he has refused to offer a referendum, in the face of calls “from the media and many inside our party.” This, Blair will say, is “real leadership” and evidence that Miliband is “his own man, with his own convictions.”

Past views

The former prime minister, who led Labour from 1994 to 2007 and won three successive election victories, hasn’t always backed Miliband over Cameron. In late drafts of his memoirs, published in 2010, he described Cameron’s coalition government as “a Tory version of New Labour.” That was changed just before publication to “a Tory version of a centrist government (whether they get that is another matter!).”

He also told the Economist magazine last year that he didn’t agree with Miliband’s strategy of moving away from a free-market position. “I am still very much New Labour and Ed would not describe himself in that way, so there is obviously a difference there,” he said. “I am convinced the Labour Party succeeds best when it is in the centre ground.” — Bloomberg