A Twitter user thought up a simple but powerful gesture to protest increased hate crimes in the U.K. after a majority of Brits voted in a referendum last week to leave the European Union.

People are showing their solidarity with immigrants residing in the U.K. by sporting a safety pin on their clothing. The idea originated with an American Twitter user known as Allison, @cheeahs, who lives in London, Mashable reports.

Allison explained the significance of the safety pin in a tweet. The idea was that "anyone against the sort of nationalistic racist violence we've been seeing could identify themselves as a 'safe' ally."

Following the controversial Brexit vote, the U.K. saw a staggering 57 percent spike in hate crimes, according to the National Police Chiefs' Council, prompting the group to issue this warning: "All forms of hate crime are unacceptable in any circumstances."

Gareth Cuerden, head of hate crimes in Wales for the charity Victim Support, told TIME:

“There are very obvious links from the outcome of the result and people using it like a catalyst to say things like ‘we are out of Europe so you now can’t be here’ or ‘go back home.'”

The #safetypin campaign is receiving an outpouring of support on Twitter and other social media sites.

"It's simple because you don't have to go out and buy it, there's no language or political slogans involved," Allison told Indy100. "It's just a little signal that shows people facing hate crimes that they're not alone and their right to be in the U.K. is supported."

Some people, however, are skeptical the campaign will elicit real change or help immigrants feel safer.