“If Britain did decide to leave, people may react on the basis that they have been told it is going to cause all these economic shocks.”
He added: “This country is the fifth-biggest economy in the world. We sit on the G7 and on the UN security council.
“We are able to prosper outside the EU and in many ways we will be liberated to do many things we are prevented from doing at present.”
Mr Whittingdale said the Remain camp should stop claiming a post-Brexit UK would have similar agreements with Europe as Norway or Switzerland, which have to accept free movement and pay into the EU budget.