LONDON (Reuters) - A giant mural of Donald Trump locked in a kiss with former London mayor Boris Johnson in the style of a legendary Soviet-era image has been unveiled by a group campaigning for Britain to stay in the European Union. Painted on the side of a building in Bristol, southwest England - home of the celebrated graffiti artist Banksy - the image reprises a 1979 photograph of Soviet leader Leonid Brezhnev and East German President Erich Honecker kissing, which was later turned into a mural on the Berlin Wall.  It was commissioned by pro-EU campaign group “We are Europe” as what they call a warning of things to come if Britons vote to leave the 28-member bloc on June 23, as advocated by both Johnson and Trump, the presumptive Republican candidate in November’s U.S. presidential election. Johnson is the “Out” campaign’s best-known leader and Trump has said Britain would be “better off without” the EU, which he has blamed for Europe’s migration crisis. The 15-foot (4.5 meter) mural is accompanied by the slogan “Not #IN for this?” and a plea for people, especially the young, to register to vote by a June 7 deadline. “People need to look at this image and think - is this the future I want,” said Harriet Kingaby, a spokesperson from We Are Europe. Galvanizing the youth vote is a key issue for the “In” camp. Surveys show young people are far more likely to be in favor of remaining in the EU but also much less likely to bother to vote. A survey of 2,000 students this month found that 63 percent did not know the exact date of the referendum, while 54 percent were not aware it was being held in June. 