Union members were due to begin 'working to rule' from last weekend, following a national ballot in response to a company-wide pay freeze announced last November. According to Unite, in the past, individual sites have been allowed to stand and fall based on their own success rather than as a whole.

Members voted to work to rule earlier this month, as opposed to full-out strike action. However, Unite national officer Steve Sibbald said he thought the two parties could come to an agreement over the action at some point today.

He said: "We are negotiating with individual sites at the moment, because working to rule means different things to different people, but we are also negotiating with Trinity and hopefully something will be agreed upon before any action has to take place.

"The company has given us certain assurances regarding bonuses, as well as assurances that next year's wage awards will be on a site-by-site basis.

"We shouldn't forget that the reason we got to this point was because the company decided to deal with the sites as a whole. If they want to return to a site-by-site basis we will do that."

Trinity Mirror has previously blasted the move, branding the plans for action as "extraordinary" because of a low turnout at the ballot box when members voted.