LONDON (AP) — The European Union is deeply flawed but remaining a member of the 28-nation bloc, "warts and all," is in Britain's best interest, opposition Labour Party leader Jeremy Corbyn said Thursday.

Britain will vote on its EU membership in a June 23 referendum — the first vote ever by a nation on whether to leave the bloc. Prime Minister David Cameron and most of his Conservative government are in the "remain" camp but several senior ministers argue that Britain should leave.

Corbyn comes from the socialist left-wing of the Labour Party and has long been seen as a lukewarm supporter of the bloc. In 1975, he voted against joining what was then the European Economic Community. His ambivalence sets him apart from many Labour lawmakers, who strongly favor an "in" vote.

In his first major speech as part of the referendum campaign, Corbyn said Thursday that the EU was not democratic enough and too eager to promote free-market policies at the expense of workers.

But he said global challenges like tax evasion, cybercrime, migrant crises and terrorism all required coordinated international efforts to fight them, and "the EU, warts and all, has proved itself a crucial international framework" for taking action.

"I remain very critical of its shortcomings, from its lack of democratic accountability to the institutional pressure to deregulate or privatize public services," Corbyn said in London. "So Europe needs to change. But that change can only come from working with our allies in the European Union."