A war of words has broken out as drivers at Elland-based paving products group Marshalls plc begin voting on industrial action.

A total of 110 drivers, members of Unite, the country’s largest union, are voting on whether to take strike action or industrial action short of a strike in a dispute about overtime pay. The ballot closes on Tuesday, May 17.

But the dispute took a new twist after Unite claimed that a manager at Marshalls’ depot in St Ives, Cambridgeshire, swore at a group of about 24 drivers while addressing them on the ballot – with all but three of the drivers walking out in protest.

Marshalls has accused the union of taking “a confrontational stance” regarding the overtime pay issue.

Unite said the dispute with Marshalls was about the disparity in overtime payments for drivers who deliver to customers from 14 manufacturing sites across the UK. Unite said the drivers receive time and a third for overtime worked, while manufacturing employees get time and a half.

Marshalls’ the two biggest customers – Travis Perkins with 1,900 outlets and Jewson with more than 600 branches – face possible disruptions to supplies if strike action goes ahead.

Unite national officer for building trades, John Allott, said the union had started balloting members, but added: “Already the tone of the dispute has turned bitter as this manager in Cambridgeshire has already allegedly sworn at a group of our members for engaging in their legitimate right to hold a strike ballot.”

A statement from the company said: “Marshalls continues to try and understand the motivations and actions of Unite the Union and the confrontational stance that Unite has chosen to take with regard to an issue as yet untabled as a ‘dispute’.

“The issue of driver’s overtime was taken off the table by the union in December as part of a wider negotiation and as yet the union has not formally communicated with Marshalls, but has chosen to move directly to a ballot.

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“Marshalls and Unite have a formal joint agreement which sets out how such issues should be handled. However, the union has chosen to ignore this.”

It added: “Marshalls is, of course, in communication with the affected employees to understand the issues raised. We understand that during the course of one such briefing heated words may have been exchanged by two individuals. Marshalls has a zero tolerance policy to workplace bullying or harassment and a very clear reporting procedure in place, However, as yet, no incident of bullying or harassment relating to this incident has been reported.”