The European Commission will move quickly to impose the “polluter pays” principle by taxing foreign firms, Commissioner-designate Paolo Gentiloni said during the European Parliament hearing on Thursday.

“We will try to be very quick and effective on a carbon border tax,” Gentiloni said.

The Commissioner warns that technical obstacles to introducing a tax are serious but not insurmountable, as legislation must be compatible with World Trade Organization rules.

The tax is meant to shield ...