Facebook mobile users jumped around 20 percent in U.S., UK in June LONDON (Reuters) - The number of users accessing Facebook via their mobile phones in June jumped around 20 percent in the United States and Britain, the social network said, touting its appeal for brands trying to reach consumers during the summer months. Created in a Harvard dorm room in 2004, the world's largest social network has moved to reposition its business for a world in which consumers' primarily access the Internet via small-screened smartphones rather than computers. The strategy has started to pay off, with the group's results for the first three months of the year showing mobile advertising revenue gaining momentum and accounting for 30 percent of Facebook's overall ad revenue in the first quarter. On Thursday, the group said its mobile monthly active users had increased by 18 percent in the United States and by 22 percent in Britain in June compared with the previous year, as brands seek different ways to reach consumers who are often on holiday and not interacting with their usual media. "We see this as a fantastic opportunity with empirical evidence of people staying engaged on mobile phones and using Facebook," James Quarles, regional director for Britain and Southern Europe, said. As people are away and on holiday, it provides a different opportunity for brands to think differently about Facebook. Though advertisers are keen to harness the boom in mobile phones, few have perfected the art of using mobile devices to target adverts to consumers, with a discrepancy remaining between the amount of time consumers spend on their mobile devices and the advertising dollars companies spend there. Facebook is seen as one of the most likely ways for mobile advertising to succeed. "When people are that engaged, checking their Facebook 14 times a day, if advertisers can deliver the right message to the right audience you can really see some business impact," Quarles said. Reporting by Kate Holton; Editing by Louise Heavens