The organiser of Womad, the world music festival, has said artists are giving up trying to visit the UK to perform because entering the country has become so “difficult and humiliating” since the Brexit referendum.

Chris Smith said the impact of the UK visa process on foreign musicians “genuinely broke his heart” and had made it more difficult to attract performers to this year’s festival.

“The world has never needed events like Womad more than it does now,” Smith told the Radio Times. “It stands for tolerance and understanding and learning and openness but that culture is being crushed as politicians lurch to the right.”

Acts from 128 countries are due to attend this year’s festival. But Smith said some had accepted the invitation to perform, only to withdraw after looking into the visa process. He blamed the situation on the 2016 decision to leave the European Union, which sent a message out that the UK was closed to foreigners.

“We’ve had situations where, say, an African artist has been due to come who plays a particularly rare instrument, and we’ll be asked: ‘Can’t you find someone in the UK who plays that instrument?’, which is absurd,” he said.

“The saddest thing is always the number of artists struggling to get visas to come and perform. What we’re seeing this year is unexpected and even more depressing, which is artists saying we’re just not going to tackle the immigration system, saying it’s too difficult and too expensive, and it’s humiliating.”

Womad (World of Music, Arts and Dance) was founded by the musician Peter Gabriel in 1982. Smith said that in recent years the festival had been helped by “good people” in the Foreign Office, but that his sense was that the situation was only going to get worse. He said he and Gabriel had spoken at length about how to support artists to continue visiting the UK for Womad.

The 36th Womad begins on Thursday at Charlton Park in Wiltshire, with headline acts including Amadou and Mariam, Django Django, Leftfield and the Herbaliser. About 35,000 people attended last year’s festival.