The RSPB will be backing the legal case of a campaign group to block a new nuclear project, after it missed the deadline to submit their own judicial review by 24 hours.

In a statement posted to their Twitter, RSPB Minsmere said: "We recently announced our intention to apply for leave to Judicial Review the government's Sizewell C decision.

"Most unfortunately, we have been informed that our paperwork was submitted a day late. With the challenging nature of the reduced time limit and having to do this over the summer holiday period, we got our timings wrong.

"We are obviously devastated, and we can only apologise to those who have supported us throughout the whole process."

RSPB operations director Jeff Knott explained the mistake, saying the team had started counting the six-week period from the day after the government confirmed development consent, rather than the day of the announcement.

"It was totally our mistake," said Mr Knott.

"We needed every single hour we could get to work on the case as we had to sift through thousands of pages and take legal advice on a project that's been prepared for the best part of a decade."

However, the silver lining for Mr Knott is that campaign group Together Against Sizewell C was able to submit their judicial review within the allotted six-week timespan.

"They will have a strong case with similar areas of concern to the RSPB," said Mr Knott.

"We wish them every success."

Mr Knott added that the entire case had to be pulled together within the six-week period, meaning new evidence could not be submitted after this point.

He said: "Usually after a planning decision is made, people have several months to submit their cases against it, but this was recently reduced to just six weeks.

"It feels to us like this entire process is stacked against those challenging the Sizewell C proposals and it also seems like EDF have been able to set and miss their own deadlines numerous times."

A spokesman for EDF Energy, the nuclear project's proposers, said: "The planning process is a clear and transparent system. Many of the deadlines set are not under our control. We have to abide by them like everyone else."

They added: "We engaged with the RSPB not only during the periods of formal consultation but much more regularly throughout the last decade.

"The deadlines are very clear for all who are involved and the only times we have extended those in our control has been to allow more time for feedback."