London - France's Economy Minister Emmanuel Macron on Thursday urged Britain to remain in the European Union, saying it was "in its interests" to protect its trade position within he bloc.Macron, a 38-year-old former banker, predicted years of uncertainty if Britain votes to leave in the June 23 referendum, and doubted it would be able to negotiate favourable trade terms from the outside."If you want an efficient and powerful relationship with the European Union, why do you want to leave the club?" he asked at a Financial Times conference on the future of Europe."You will take two years to renegotiate something new, for what? The sort of relationship that Norway or Switzerland have," he added."Don't forget that they contribute to the budget to get access, and not even to the full fledged single market."I do believe that the British interest is to remain in the EU," he concluded.The referendum campaign period formally kicks off on Friday with latest polls suggesting a dead heat.