Some of the UK’s most garlanded novelists, including Robert Harris, John le Carré and Philip Pullman, have lambasted the promises made by Brexiters as being too unbelievable for fiction, writing: “We are the people who spend our lives making things that are not true seem believable, and we don’t think Brexit is even a good effort.”

Dozens of writers have put their names to a letter to the Guardian that urges UK voters taking part in Thursday’s European parliament elections to use their franchise to support the European Union, “unless they know what they are choosing to lose, for themselves and everyone they know, and are happy with that”.

The authors, who also include Neil Gaiman, Nikesh Shukla, Kate Williams and Laurie Penny, go on to say: “It seems to us that the same question is facing every industry and every person in the UK: what will you choose to lose? Because we used to hear about advantages in Brexit. We used to hear about the bright future, the extra money, the opportunities. Now the advocates of Brexit just assure us that it won’t be as bad as the last world war.”

The letter adds that – like everything from the NHS to the British car industry – authors’ output will be affected by Brexit: book exports account for 60% of UK publishing revenues, with 36% of physical book exports going to Europe. “It’s fashionable among politicians to sneer at the creative industries, but our work is work just like anyone else’s, and like anyone else’s it can only happen if we get paid. Without any idea of what Brexit might look like, it’s impossible to know exactly what we might lose. A tenth? A fifth? A third of what we live on?” they say.

Novelist Nick Harkaway, who worked with Suw Charman-Anderson, the founder of Ada Lovelace Day, to bring the letter together, said it had happened almost by accident. “Almost all the writers and creative industries people I know are desperate over Brexit. It’s such a waste and such a mess,” he said.

The response, he said, was enthusiastic and immediate. “Ironically, for a bunch of communicators, I think we’d all been feeling gloomy and pent up. And maybe it’s close to home, too: writing is all about putting an idea into solid form. We know what that process looks like when it’s going to work. We also know how hard it is to reject something that won’t work once you’ve started down that road, but sometimes you still have to do it. So here we are,” said Harkaway.

“We thought of addressing Jeremy Wright MP at the DCMS, but the government is closed off on Brexit. It cannot – I think we have to say ‘it dare not’ – hear all the voices saying ‘Stop!’. Why would you write to someone you already know isn’t going to pay attention? And Parliament is log-jammed. So it comes down to people, and news media, and voting. People have to go out and vote for what they want, tell their MPs and MEPs, tell the parties, tell one another.”