MPs have been promised the sister project of a proposed third nuclear power plant on the Suffolk coast will go ahead despite a fresh delay in making a final investment decision.

EDF’s chief executive assured the government that money was in place for Hinkley Point C, and that “no project had been better prepared” – but he meanwhile remains locked in talks with French trade unions over the impact of the firm’s finances on pressing ahead with the development in Somerset.

Vincent de Rivaz, head of the French energy giant, told the Energy and Climate Change Committee he was confident the Hinkley Point nuclear power station will go ahead – paving the way for the £16 billion Suffolk project.

Consultation with trade unions began on May 2, after some called for a delay of two to three years before the firm decides to go ahead with its project to build the two nuclear reactors.

The talks could take 60 days to complete, according to Mr de Rivaz, who said he wanted a final decision to be taken “the sooner the better”.

In March, he told the same committee that Hinkley Point would definitely go ahead, pointing to a speech by French economy minister Emmanuel Macron that the final investment decision would be made in early May. But Mr Macron later said the green light may not be given until September.

In a letter to the committee, Mr Macron said that owing to the importance of the project, EDF had decided to promote “exemplary labour/management dialogue” by consulting the Central Works Committee on the project.

The French authorities remained “fully behind” Hinkley, said Mr Macron, adding: “I can appreciate that a certain amount of impatience may be creeping in as the project is key for the UK’s energy and climate policy.

“It is also necessary, in the interest of all, that EDF follows due process before committing itself to an investment of this magnitude. The consultation of the Central Works Committee brings legal robustness on the decision.

“I have every confidence that a final investment decision can be made rapidly after the end of the consultation of the Central Works Committee and that it will signal the development of a very fruitful collaboration in the industrial and energy sectors between our two countries.”

Mr de Rivaz insisted the project was not on hold, and “everything was set” for power to be generated by 2025.

Pressed on the timing of a final investment decision, he said it would be “very rapid” after the 60-day consultation with French unions.

He appeared before the committee alongside EDF’s nuclear new build managing director, Humphrey Cadoux-Hudson, and energy minister, Andrea Leadsom, who told the MPs that the Government was “fully confident” that the Hinkley project will go ahead, and that it was “quite right” that EDF wanted to consult its workforce, she added.

Greenpeace has called for the UK Government to “wake up” to the alternatives. Chief scientist, Dr Doug Parr said Hinkley would remain uncertain while similar reactor design projects in Finland and France were “over budget and delayed by years”.

The minister said no single project would destabilise the UK’s energy system and pledged that the Government would not allow the lights to go out.