The supermarket giant threatened earlier this month to tear up a bargaining agreement with the GMB general union at its Dartford centre in Kent.
The move comes a fortnight after it was forced to pay£850,000 to another group of employees at Washington, Tyne and Wear, by Newcastle Employment Tribunal. It unlawfully offered a financial inducement for employees to vote away the union's negotiating powers there.
A GMB spokesperson said: 'Management is trying to introduce a modern collective agreement in Dartford that will water down our ability to represent our members.'
A senior Asda manager warned that the union will be 'derecognised' by the end of this week if it fails to sign up to the new arrangement.
A letter on February 6 from Asda's head of industrial relations for the distribution network Marie Gill, to GMB regional officer Jeff Goswell, said: 'Discussions have progressed but have gone well beyond the timescales agreed. Unless we can make substantial progress within the next four weeks in negotiations concerning the new arrangement proposed for Dartford, the existing collective agreement between the GMB and Asda will have to be terminated.'
An Asda spokesperson said: 'We've been in discussions with the GMB since last April about a more modern collective agreement and we're confident that we'll reach agreement by the end of February, as is the GMB regional officer.
'The old agreement needs updating, it's so old, (a Christian Salvesen document that hasn't been updated since 1996) and includes elements that are illegal. For example, it doesn't reflect new legislative obligations on disciplinary procedures.
'All along, we've been quite clear that the aim of our discussions is to update our collective agreement. We have no wish to move away from it. All we've done is say that we don't want negotiations to drag on for another 10 months.'
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