Budget cuts at Sellafield increases the risk of “devastating consequences” at the world’s biggest plutonium stockpile, the GMB union has warned.

In a letter written to Chancellor Rachel Reeves ahead of the Budget next week, the GMB warns of the “risks posed by reducing funding for such a complex and hazardous site”.

Sellafield, on the coast of Cumbria, is the UK’s most complex and challenging nuclear site. The scale of the decommissioning operation is vast and will last until 2039.

Just last week a new National Audit Office report found that progress on the site is slow and is “not yet achieving value for money.”

The site is owned by the Nuclear Decommissioning Authority (NDA), which is an executive non-departmental body sponsored by the Department of Energy Security and Net Zero.

The letter, written by Roger Denwood, GMB Sellafield branch secretary, and Denise Walker, GMB regional secretary, urges Reeves not to reduce the budget for the taxpayer-owned NDA.

The letter says that Sellafield...