The GMB has narrowly lost its historic bid for union recognition at the Amazon warehouse in Coventry.
Some 49.5% of workers balloted voted in favour, while 50.5% voted against. The union needed a majority to vote in favour.
If the GMB had won it would have been the first time Amazon recognised a union in the UK.
The online giant would have been forced to negotiate with workers on issues such as pay and conditions.
In a statement, Amazon said it placed “enormous value on engaging directly” with staff.
“We look forward to continuing on that path with our team in Coventry,” it added.
The GMB said its drive for recognition fell “agonisingly short” and accused Amazon of “union-busting”.
It said there were “anti-union messages by company bosses, including multiple anti-union seminars” at the warehouse.
It added that “the fire lit by workers in Coventry and across the UK is still burning”, and that the union would “carry on the fight” for low paid workers.
The union’s fight for recognition had been described as a David vs Goliath battle, with workers facing fierce resistance from the online giant.
It began with a rag tag show of defiance in the summer of 2022, after Amazon offered workers a pay rise of between 35p and 50p an hour.
Having toiled in warehouses during the Covid pandemic, workers said this felt like an insult, and in Coventry a small group of angry workers spontaneously walked out and protested outside the fulfilment centre.
Then the GMB got involved and urged the workforce to unionise.
In January 2023, with a GMB membership of just 50, Coventry workers held the first ever Amazon strike in the UK.
It went on to organise a further 37 days of industrial action over the last year and by recruiting on the picket line, steadily built up its membership to more than 1,400 members out of the centre’s estimated 3,000 plus workers.
In April the union launched a legal challenge against Amazon, claiming it used underhand tactics to encourage members to cancel their union membership.
On Wednesday it said that legal challenge would continue.