By Andy Bruce(Reuters) - Britain's Conservative Party will introduce mandatory national service for 18-year-olds if it wins the national election on July 4, comprising military or community participation, Prime Minister Rishi Sunak said on Sunday. The announcement followed Labour Party leader Keir Starmer's comments on Saturday that he was in favour of allowing 16 and 17-year-olds to vote. Sunak's Conservatives lag Labour by a wide margin in opinion polls, which have shown little change in fortunes for the prime minister since his surprise election call last Wednesday. That is why we will introduce a bold new model of national service for 18-year-olds," Sunak said in a statement. "The national service we need from our young people is to vote for change on 4th July," said Andy Burnham, mayor of Greater Manchester.