RWE and E.ON announced today that they will be abandoning their plan to build nuclear reactors in the UK, citing financial difficulties. The two were planning to invest in new plants in Anglesey and Oldbury under Horizon Nuclear Power, a joint venture created specifically for the UK project.

RWE said in a statement. “RWE and E.ON will now focus on finding a new owner for Horizon Nuclear Power.”

According to the GMB Union, the move is a “devastating blow” to the UK’s energy future.

“New nuclear is an essential component in keeping the lights on in the UK,” the GMB’s Gary Smith said. “We can’t keep extending the lifespan of existing nuclear stations and renewables cannot fill the gap on their own.”

Through the Horizon joint venture, RWE and E.ON were planning investments of about £15 billion ($23.83 billion) in around six gigawatts of new nuclear by 2025.

While the government says it is disappointed, there remains “considerable interest” in the project.

“E.ON and RWE’s withdrawal is clearly very disappointing, but the partners have clearly explained that this decision was based on pressures elsewhere in their businesses and not any doubts about the role of nuclear in UK’s energy future,” Energy Minister Charles Hendry said. “Plans from EDF/Centrica and Nugen are on track and Horizon’s sites offer new players an excellent ready-made opportunity to enter the market.”

In response, both Westinghouse and EDF issued statements expressing their continued support of UK nuclear energy. Westinghouse had been in the running against Areva for the contract to build the reactors for the sites.

“Although very disappointed with this decision, the Westinghouse resolve and commitment to the United Kingdom and its nuclear industry is unshaken,” the company said. “We strongly believe that the AP1000 technology is ideally suited to the Wylfa and Oldbury sites and elsewhere in the UK and Europe.”

EDF, who currently has plans for two new nuclear reactors at Hinkley Point in the works, also reiterated its commitment.

“EDF Energy and Centrica remain focused on our project and nothing has changed with regard to that. We are determined to make U.K. new nuclear a success,” a statement from the company said.