Royal Mail has clashed with the main union representing postal workers as they staged another strike in the long-running dispute over jobs, pay and conditions.

The company said it has written to Dave Ward, general secretary of the Communication Workers Union (CWU), claiming a pattern of “wholly unacceptable behaviour” on picket lines across the country.

The union strongly denied the allegations, insisting that picketing since the start of strikes has been peaceful.

Royal Mail said more than 100 allegations of incidents including violence and harassment have been reported over the four months of the CWU’s industrial action, with 35 cases reported to the police.

Royal Mail strike
The Royal Mail Islington Delivery Office was closed due to strike action (Belinda Jiao/PA)

A Royal Mail spokesperson said: “This behaviour has no place in any civilised workplace. The direct intervention of the CWU’s general secretary is needed to end this culture of intimidation on the picket line, including many incidents by CWU representatives.

“More than 10,000 frontline employees chose to work on each of the last two days of strike action, and with numbers increasing with each passing day of industrial action, they should feel confident that they can do so safely and without the risk of harm. We have zero tolerance for bullying or harassment.

“We will continue to support any employee who works on a strike day. They can be assured that we will investigate every incident and allegation and take swift action to discipline the individuals involved appropriately.”

Royal Mail said it had reported picket line incidents to police in Scotland, Northern Ireland, West Midlands, Lancashire, London, Kent, Norfolk, Devon & Cornwall, and Gwent.

A CWU spokesperson said: “These allegations are as embarrassing as they are untrue. For a chief executive who spends his every waking hour, intimidating, gaslighting and mocking our members online, to have the front to target others for wholly legal and friendly picketing is beyond a joke.

“Prior to every round of strike action, the union has reminded members to turn out in record numbers whilst being peaceful and respectful. Our members and reps have done us proud.

“Our members want to go back to work and save Christmas for 32 million households in the UK but they will not bow down to a culture of intimidation.”

More strikes are planned in the coming weeks, including on Christmas Eve.