LONDON (AP) — If celebrity power were votes, Britain's European Union membership would be secure.

Almost 300 actors, writers, musicians and other cultural figures appealed Friday for British voters to back the "remain" side in a June 23 EU membership referendum, arguing that a vote to leave the 28-nation bloc will leave the U.K. "an outsider shouting from the wings."

Signatories from the acting world included "Sherlock" star Benedict Cumberbatch, "X-Men" superhero Patrick Stewart, Jude Law, Bill Nighy, Keira Knightley, Kristin Scott Thomas, Chiwetel Ejiofor and Helena Bonham Carter.

They were joined by spy novelist John le Carre, "Wolf Hall" writer Hilary Mantel, fashion designer Vivienne Westwood, "Slumdog Millionaire" director Danny Boyle, singer Paloma Faith and the members of rock band Franz Ferdinand.

The letter said many creative projects "would never have happened without vital EU funding or by collaborating across borders." It argued that Britain's creative success "would be severely weakened by walking away."

"From the Bard to Bowie, British creativity inspires and influences the rest of the world. We believe that being part of the EU bolsters Britain's leading role on the world stage," the signatories said. "Let's not become an outsider shouting from the wings."

Culture is one of Britain's biggest exports. Data released Friday by the British Phonographic Industry showed than one in six music albums sold in 2015 was by a British act, and U.K. actors regularly headline Hollywood films.

Prime Minister David Cameron underscored the artists' "remain" message with a visit Friday to London's Abbey Road Studios, where the Beatles once recorded. He met signatories to the letter including "The Wire" star Dominic West and sculptor Anish Kapoor.

Most of the generally liberal arts community backs remaining in the EU, but the support is not absolute. Brexit-backing entertainers include actor Michael Caine and singer Roger Daltrey of The Who.

Writer and Conservative peer Michael Dobbs — who wrote the original British 1990s series "House of Cards" — said Britain's creative industries were booming "because of the talent that is in Britain's DNA," and not because of the EU.

The EU, Dobbs said, is "failing. The dream is dead. We need to move on."