Officials from energy giant EDF are being called back to Parliament to explain to MPs a further delay in the Hinkley Point nuclear power station.
The Energy and Climate Change Committee said it wanted to question senior representatives from the French firm about the long-awaited final investment decision on the £18 billion project.
Chief executive Vincent de Rivaz told the committee last month that Hinkley Point would definitely go ahead, pointing to a speech by French economy minister Emmanuel Macron that the final investment decision will be made in early May.
But Mr Macron said at the weekend that the green light may not be given until September.
Angus MacNeil, chairman of the Energy and Climate Change Committee, said: "When EDF appeared before us in March, company bosses were insisting that a decision would be made in May.
"At that hearing we said that we would call them back in if that timetable slipped again and that's what we are doing now.
"If Hinkley does not go ahead it could have huge implications for our future energy security and efforts to cut climate-changing emissions.
"We will therefore be watching progress on this closely. If we have to see EDF back here in September as well, we will."
Dates and times for the hearing will be confirmed in due course, but it is expected to take place in late May.
Mr de Rivaz told MPs in March that the project had successfully passed regulatory, political, commercial and operational milestones.
EDF had invested £2.4 billion in the project and continued to spend £55 million a month, he said.
Asked about a date for the long-awaited final investment decision, he said it would be "soon".