MEGA-RICH Amazon is using “dirty tricks” to bust union organising, GMB charged today after it was forced to withdraw a historic push to win recognition at the online retail giant’s Coventry warehouse.

During months of groundbreaking pay strikes, the general union’s membership at the site has skyrocketed from about 60 to more than 800 — well over half the 1,400 employees that Amazon said worked there last year.

But as GMB made an official application to the Central Arbitration Committee (CAC), which can force bosses to recognise unions if they represent more than 50 per cent of the workforce, the US-owned firm “flooded” the warehouse with 1,300 new staff, the union said.