Hundreds of strikers outside Amazon’s Coventry warehouse in the U.K. were joined on Black Friday, which this year fell on November 24, by trade unionists from Europe and the U.S. as part of a global campaign calling for better working conditions at the internet retailer.

The Guardian reports that organizers at the GMB Union in Coventry, where workers first took strike action in January, say they have now signed up 1,200 members.

They made a formal bid for union recognition to the independent Central Arbitration Committee (CAC) this year, believing they represented more than half of the workers in Coventry. They subsequently withdrew the application, accusing Amazon of hiring up to 1,000 extra workers to “bust the union” after the CAC was understood to confirm Amazon’s claim that there were 2,700 staff on site. They are now considering a fresh application.

Alke Bössiger, the deputy general secretary of the UNI global union, which is one of the co-convenors of the Make Amazon Pay campaign, said 150 actions against Amazon were taking place in more than 30 countries on November 24. 

The U.S. regulator the Federal Trade Commission is engaged in a lawsuit against the company, accusing it of anti-competitive practices – something Amazon has denied.