A senior British Cabinet minister says the U.K. would still be part of a free-trade zone with the European Union if it votes to leave the bloc.

Justice Secretary Michael Gove, a leader of the campaign to leave the EU, said Tuesday that "outside the EU we would still benefit from the free-trade zone which currently stretches from Iceland to the Russian border, but we wouldn't have all of the EU regulations" and associated cost.

Supporters of staying in challenge that view, saying countries such as Norway and Iceland have had to agree to abide by EU rules in order to be admitted to the free-trade zone.

On Monday, the Treasury said quitting the EU would leave the British economy 6 percent smaller by 2030.