Workers at two of the company’s centres in Staffordshire and Nottinghamshire are to vote on possible action over pay.
More workers at online giant Amazon are to be balloted for strikes over pay.
The GMB said its members at Rugeley, in Staffordshire, and Mansfield, Nottinghamshire, will vote in the next few weeks on whether to launch a campaign of industrial action.
The GMB has already held a series of strikes at Amazon’s site in Coventry, which the union said is having a “domino effect” in other areas.
Workers have since submitted a request for union recognition after the GMB reached the membership threshold for mandatory recognition, which it said could mark Amazon’s first union recognition in Europe.
The ballots at Rugely and Mansfield will run until June 9.
Amanda Gearing, GMB Senior Organiser, said: “This is no time for sound bites; but Amazon workers are fighting back against a pay rise of pennies from one of the world’s wealthiest corporations.
“This escalation will see workers in two further fulfilment centres asked to have their say on downing tools and walking out to deliver pay justice.
“We’ve already seen enormous enthusiasm from workers at Mansfield and Rugeley to take action, now it’ll be up to them how their union moves forward with the campaign.
“We warned Amazon that this could fast become a summer of strike chaos if they refused to sit down and talk pay. Amazon Coventry workers have risen up, now we are seeing a domino effect.
“With strike action escalating and historical union recognition on the horizon, it’s time for Amazon to get real and get around the table”.
