Sellafield has temporarily stopped work on the Silos Direct Encapsulation Plant while an “engineering review” is carried out.

The move means main subcontractors Vinci and Nuvia could have to lay-off up to 100 workers.

A Sellafield spokesman said: “We are aware that our decision is likely to have an impact on the number of contracting staff working on the project and the main sub-contractors Vinci and Nuvia have today taken steps to inform their workforces that redundancies are likely.

“Although issues such as these are common in contracting work, it is always regrettable when jobs are at risk.

“We will be working closely with Vinci and Nuvia over the coming days and weeks to establish how our decision will impact their workforce but our initial understanding is that there may be up to 100 people involved.”

The spokesman added: “We are currently undertaking an engineering review of a complex project which is at an important point in its development to ensure we proceed into the next stage on a strong basis.

“As part of this review, construction work on the project has been temporarily suspended while we focus our attention on design engineering work.

“This decision has not been taken lightly, it is entirely the responsibility of Sellafield Ltd and has been made to ensure we focus our resources on essential engineering work on the project. We have a duty to ensure we provide value for money for the taxpayer.

“It is in no way a reflection on the performance of the contractors who have been working hard to accelerate the site based work on the project over recent months.”