High Court to hear arguments for legal challenge to Sizewell C plans

TASC says that plans for additional flood defences at the power station were omitted from the original application for a development consent order (DCO), and could result in a negative impact on local wildlife.

In an oral permission hearing today 9 December 2025, the group will argue the additional barriers could disrupt nearby protected areas of wildlife, and that alternative and less disruptive options were not properly considered.  

The power station was granted development consent in July 2022. Plans for the station included a revetment stone wall and a sacrificial shingle bank to act as coastal flooding defences, along with the power station being built on a raised platform.  

Provisions were also included to increase the height of the revetment walls should the risk of a breach increase due to rising sea levels. 

However, in April 2024 a report from the Office for Nuclear Regulation (ONR) revealed that the planned coastal defences for Sizewell C would not be sufficient to protect it in a worst-case scenario for sea levels rising.  

The report also showed that this information had been known since 2015, prior to (but absent from) the DCO application, and revealed that developer Sizewell C Ltd had made provisions to build additional flood barriers further inland to protect the power station.  

TASC says that there is clear potential for the additional barriers to impact nearby protected areas of wildlife, and that options for less invasive flood defences were discarded.  

The group wrote to Secretary of State for Energy Security and Net Zero Ed Miliband (SoS) in March 2025 asking that he consider revoking or changing the DCO, so that the environmental impacts of the project could be re-assessed. 

This request was not accepted, however, and TASC consequently filed for a judicial review claim in June challenging this decision. TASC will now argue in a permission hearing that:  

• The SoS was in breach of his obligations under the Habitats Regulations Act 2017 when refusing TASC’s request to review the development consent order. 
• The SoS misdirected himself in law in the justification for the response to TASC’s request. 
• The SoS breached his duty of inquiry in his refusal of TASC’s request. 
• The decision to refuse TASC’s request to vary or revoke the development consent order was irrational. 

Chris Wilson, on behalf of TASC, said: 

“With the coastline in front of the site already eroding, even before the plant has been built, TASC is alarmed that Ed Miliband is risking billions of public funds on Sizewell C in the full knowledge that the project, as approved in the development consent order, is not resilient to extreme sea level rise and is happy to burden future generations with the financial and environmental responsibility to keep the site and its spent fuel safe till the late 2100s. Denying public scrutiny now and choosing to 'kick the can down the road' could eliminate consideration of the most viable options for future site safety." 

Leigh Day solicitor Rowan Smith, who represents TASC, said: 

“Our client is concerned about the revelation that provisions have been made for further flood defences at Sizewell C, which could harm the environment, yet the impact of this has never been assessed. This is alarming, given the potential risk to protected species, including the Marsh Harrier, as well as the burden placed on future generations to resolve the issue. TASC argues that the Secretary of State must at least lawfully review, in line with the Habitats Regulations, whether the development consent order granted for the Sizewell C project should be amended.”