Nuclear chiefs are under fire after it emerged that plans for a new power plant have slipped.

The consortium behind proposals for three reactors near Sellafield have admitted there will be a one-year delay in the first becoming operational.

It's an admission that anti-nuclear groups claim will "wreak havoc" for the entire £10bn Moorside vision, the largest project of its kind in Europe and a major plank of Cumbria's financial future.

NuGen, which is leading the proposal, has previously stated that the first of the three reactors would be operational by 2024.

But documents released to the public for the first time this week show that the first AP1000 reactor is now not expected to produce power until the end of 2025.

Campaign group Cumbrians Opposed to a Radioactive Environment (Core) claims the delay is NuGen's "belated realisation that its original timetable was just pie in the sky". 

NuGen, however, says that the start date was planned many years in advance and the newly-announced date change is due to elements "out of its control".

The plans - on which the public is currently being consulted - are due to be submitted, says NuGen, for final financial and planning approval in 2018, with construction due to start two years later.

But Core spokesman Martin Forwood said: "The delay will wreak havoc with the timetable for building the second and third reactor; the latter originally scheduled for completion by 2026.

"The timeline is slowly but surely marching backwards and west Cumbria needs to wake up to that reality."

New villages to house thousands of construction workers will need to be created, along with new stretches of railway to ease pressure on already congested roads such as the A595, when the reactors are being built.

Mr Forwood described NuGen's plans as "staggering in scope".

He added: "The period of major disruption and sheer misery caused to many locals by these combined works will now be extended."

A NuGen spokesman said: "The Moorside project is still in the development phase and we remain on track to achieve the final investment decision in 2018. 

"Beyond that, there are elements of the project which are out of our control and NuGen believes it is more appropriate to refer to the target date for Moorside site delivering power as the mid-2020s."

Once completed, Moorside would be capable of producing up to 3.8 Gigawatts of electricity, enough to power six million homes and supply 7.5 per cent of the UK’s electricity needs. NuGen has signed a deal to export most of that to the National Grid.