image sourceReutersimage captionThe Retail, Wholesale and Department Store Union wants to set up a branch at Amazon
An official examining a landmark Amazon union election in Bessemer, Alabama, has recommended a rerun.
The officer, from the National Labor Relations Board (NLRB), had been looking into the legitimacy of April's vote.
Amazon appeared to have stopped a union from forming, winning a vote on the issue by a margin of two to one.
However the Retail, Wholesale and Department Store Union (RWDSU) alleged that Amazon had illegally pressured its workers.
The NLRB has the power to force a rerun.
Stuart Appelbaum, President of the RWDSU, said: "Amazon's behaviour throughout the election process was despicable.
"Amazon cheated, they got caught, and they are being held accountable."
The union specifically alleged that employees were pressured to drop ballots into a mailbox that was in view of Amazon cameras.
It was claimed Amazon was trying to create the perception of surveillance.
Amazon had said the post box was installed to give workers easier access to voting.
Amazon said it planned to appeal.
"Our employees had a chance to be heard during a noisy time when all types of voices were weighing into the national debate, and at the end of the day, they voted overwhelmingly in favour of a direct connection with their managers and the company," Amazon said in a statement.
The campaign to unionise had drawn implicit support from President Biden, along with celebrities such as Danny Glover.
Workers in Alabama – and all across America – are voting on whether to organize a union in their workplace. It’s a vitally important choice – one that should be made without intimidation or threats by employers.
Every worker should have a free and fair choice to join a union. pic.twitter.com/2lzbyyii1g
— President Biden (@POTUS) March 1, 2021
The BBC is not responsible for the content of external sites.View original tweet on Twitter
The decision does not mean a rerun will definitely happen.
In the coming weeks, a regional director for the NLRB will decide whether to order another vote based on the recommendation.