George Osborne blocked moves intended to provide extra protection for the Hinkley Point nuclear plant from potential national security threats posed by China, a former cabinet minister has claimed.
Lib Dem ex-energy secretary Sir Ed Davey said no explanation was given for the then chancellor's decision to reject a pivotal "special share" in the Somerset project.
"Concerns on Chinese involvement didn't stand up to scrutiny last time round, but if the Treasury had adopted my proposal for a special share we could have included extra safeguards. But Osborne rejected it without explanation," Sir Ed told the Daily Telegraph.
The proposed special share in the consortium would have enabled the Government to intervene on certain decisions to protect the national interest, Sir Ed said.
The claim came after Prime Minister Theresa May was accused of having a "suspicious approach" to dealing with China in the Hinkley Point nuclear project controversy.
Liberal Democrat former business secretary Sir Vince Cable said Mrs May was against relaxing visa requirements for visiting Chinese businessmen when she was home secretary and had to be overruled by Mr Osborne.
Sir Vince suggested Mrs May had a "general prejudice" against Chinese investment due to national security concerns.
"It came up in all kinds of different ways. Osborne kept pushing for more liberal treatment of visas for Chinese businessmen and she was very reluctant to go along with that. So I think she has form in adopting a more suspicious approach, more in line with the American position," he told the Sunday Telegraph.
"My recollection was that when approval was sought for Hinkley, she raised objections on the grounds of national security issues with China.
"She has expressed, in several different contexts, severe reservations about China getting too close to the UK."
Mrs May caused shock in the business world when she ordered a last-minute halt to finalising the £18 billion Hinkley Point project so the situation could be reviewed.
Sir Vince said the new Prime Minister's more critical approach was right "once you separate that out from a kind of general prejudice against Chinese investment".
He said Mrs May was unhappy with what she saw as the Government's "gung-ho" approach to doing deals with Beijing when they were in cabinet together during the coalition.
Another factor in Mrs May's delay may be fear of a backlash over prices due to the unusually large amount of money French energy giant EDF will be paid for generating power from Hinkley - £92.50 per megawatt hour of electricity generated.
Security concerns centre on the one-third stake the Chinese state has in the massive project.
Labour leader Jeremy Corbyn described the price levels involved as "disturbing" as he backed a review. But the boss of EDF, Vincent de Rivaz, has tried to calm the fears of workers by insisting he understands why Mrs May wanted more time to consider the project, while insisting the deal was still "strong".
The company's board voted narrowly to give the final go-ahead for the long-delayed project but the Government pulled back from signing the contract, saying it would make a decision in the early autumn.
Downing Street will not comment on Sir Vince's claims, while Business and Energy Secretary Greg Clark insists the Government will "carefully consider" all the component parts of the project.
Meanwhile, Financial Times reported that Treasury minister Jim O'Neill could quit the Government over Mrs May's new approach to China.