LONDON—As it enters its final year of European Union membership, the U.K. looks set to be the slowest-growing economy among its rich-country peers, with uncertainty over its future expected to prevent it from reaping the full benefits of the global upswing.
Prime Minister Theresa May toured the U.K. on Thursday to mark a year to go until the country officially leaves the bloc on March 29, 2019. In a statement released by her office, she painted Brexit as an opportunity to boost Britain’s economy by freeing it from EU rule...