The deal was secured after meetings between union officials and the 14-strong group of Sellafield subcontractors earlier this week, with the unions now confirming a “full withdrawal of all industrial action”.

The new convener will investigate workers’ welfare and health and safety issues, as well as acting as a link between the unions and subcontractors.

The deal will also see the formation of a health and safety committee spanning all Sellafield subcontractors.

The subcontractors include Cape Industrial Services, Focus Scaffolding, Hertel UK, Interserve Industrial Services, Jacobs Stobbarts, Meldrum, Mitie Facilities Services and PPS Electrical.

Amec Foster Wheeler, Balfour Beatty Engineering Construction Services, Doosan Babcock, Nuvia, MW Hargreaves and PC Richardson & Co make up the remaining subcontractors.

The agreement comes after nearly six months of action by union members who had raised health and safety concerns.

This has led to more than 16,000 hours of work being lost at the site.

On 5 August, more than 1,200 workers stopped working for two-and-a-half hours in protest at the absence of a full-time convener.

This was followed by a second strike on the 19 August, which saw more than 1,000 workers walk out for two-and-a-half hours.

Four more strikes followed in September, including a 24-hour walkout on 23 September.

A work-to-rule and overtime ban was also put in place by the unions on 31 July.

Unite senior shop steward at Sellafield Ryan Armstrong says: “Common sense has prevailed, unions are there to help and support their workers and this news means the workers have a voice now.

“Now that we have an individual and group that will be investigating any problems with health and safety and workers’ welfare, it means we have a channel now to the subcontractors’ representatives.

“We have achieved the two main things we were going for and this can only help the site going forward – it will nip problems in the bud at source.”

Unite regional secretary for the North-west Mick Whitley said: “A healthy workplace is a more productive workplace.

“The creation of a new senior shop steward on maximum facility time at Sellafield will help make the site safer, reduce accidents and enable workforce issues to be dealt with speedily.”

A Sellafield Ltd spokeswoman explained “We welcome the fact that the contracting companies and their employees involved in this dispute have reached an agreement, and can now focus on delivering progress at the site.

“Sellafield Ltd and our employees are not directly involved in the dispute, which is in no way related to the safety of the Sellafield site. The dispute concerned the nature of union representation for the contractor community.”

The NAECI Sellafield contractor group would not comment on the news.