Britain's opposition leader, Jeremy Corbyn, says Britain should stay in the European Union, arguing that "a vote to remain in is in the best interests of the people of this country."

Corbyn comes from the socialist left-wing of the Labour Party and has long been seen as a lukewarm supporter of the 28-nation bloc. In 1975, he voted against joining what was then the European Economic Community.

In a speech Thursday, Corbyn said 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 actions to fight them, making "the EU, warts and all" an important vehicle.

Britain will vote on its EU membership on June 23.