The GMB claims to have signed up hundreds of new members among the workforce at Coventry and in Amazon sites further afield since the dispute began.
More than 560 workers are now expected to join in two three-day stoppages, one from 16-18 April and another from 21-23 April. Previously fewer than 300 staff were involved. The union believes it is edging closer to the 50% membership that would allow it to apply for statutory recognition.
The GMB will also gauge the appetite for strike action among other Amazon workers by holding consultative votes at another five distribution centres: Coalville and Kegworth, both in Leicestershire; Mansfield in Nottinghamshire; Rugeley in Staffordshire; and Rugby in Warwickshire.
If these votes yield positive results, formal strike ballots could then be held.
The dispute in Coventry began with an informal walkout last summer, after staff were told they would receive a pay rise of 50p an hour. Some felt this did not give sufficient recognition of the fact they had worked throughout the pandemic. By the end of April they will have taken 14 days of strike action.
The strikers have received the support of the local MP, Taiwo Owatemi, as well as US-based union activists who have been pressing for recognition at Amazon sites.
Amazon, which does not voluntarily recognise or negotiate with unions, has pointed out that the Coventry dispute involves less than 1% of its total UK workforce.
