A ballot for strike action among drivers at paving group Marshalls is underway.

The dispute, which the Unite union has claimed will “severely hit” the company’s two biggest customers, Jewson and Travis Perkins, centres on overtime payments.

It claimed there is a disparity between the drivers, who receive time and a third for overtime worked, and manufacturing employees, who receive time and a half.

A total of 110 drivers are voting on whether to take strike action or industrial action short of a strike, with the ballot closing on Tuesday 17 May.

Unite claimed that a manager at the St Ives depot in Cambridgeshire swore at a group of about 24 drivers while addressing them on the ballot, with all but three walking out in protest.

John Allot, Unite national officer for building trades, said: “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.

“We urge Marshalls not to verbally threaten or intimidate our members.”

In a statement from Susie Fehr, Marshalls group HR director, she said the issue of drivers’ overtime had been “taken off the table” during wider negotiations with the union in December.

She added: “As yet the union has not formally communicated with Marshalls, but has chosen to move directly to a ballot.

“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.”

Fehr said that the company understood that during a 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.”

Travis Perkins said it would not comment; a spokeswoman for Jewson said: “We are aware of the industrial relations issue at Marshalls but as this is an ongoing matter between Marshalls and its employees it is not appropriate for us to comment at this time.”