British opposition leader Jeremy Corbyn has urged voters to remain in the European Union — but slammed the bloc's planned trade deal with the United States, saying it threatens employment rights and hands power to "giant corporations."

Corbyn says his Labour Party will veto the Trans-Atlantic Trade and Investment Partnership if it forms a government.

But he supports EU membership for Britain, saying that has raised standards for workers, protected the environment and bolstered human rights.

Some "remain" campaigners have criticized Corbyn for not making a louder case for EU membership ahead of the June 23 referendum. The socialist Corbyn opposed Britain joining the bloc in a 1975 referendum.

Corbyn says Thursday that "Europe needs to change ... but those changes can only be achieved by working with our allies."