Prime Minister Boris Johnson must give approval for a pioneering Rolls-Royce mini nuclear-reactor project in the next six months or risk delaying a project vital to his green-energy revolution.
Rolls will be unable to meet a target of deploying its first reactor by 2029 unless ministers place an order before the end of the year.
That is the message from Tom Samson, the Rolls chief executive at the project.
The company's small modular reactors (SMRs) are expected to play a key part in the Prime Minister's plans for an energy revolution.
The Telegraph says Mr Johnson is extremely "gung ho" about nuclear and wants it to generate about a quarter of the UK's power by 2050.
This deadline is considered to be extremely tight, and any delay for Rolls would potentially have a severe knock-on impact.
Mr Samson said: "If we do not have an instruction to deploy our technology in the UK by the end of this year, then our ability to meet 2029 will move back accordingly."
Harnessing nuclear-submarine technology
Rolls, one of the UK's largest engineers, is leading a group of investors aiming to harness its nuclear-submarine technology, used by the Royal Navy to power vessels for a decade at a time.
The company hopes that its SMRs will be bought individually by heavy industry customers to power their factories, or grouped together for domestic generation with output comparable to a traditional reactor.
Each SMR is expected to cost £1.8billion and take up about 10 acres of space. They would generate about a seventh of the power of Hinkley Point C, but only cost a twelfth of the price.
Rolls has shortlisted six sites south of the border as potential hosts of a factory where it intends to build the reactor vessels central to a nuclear power plant's construction.
Russia's attack on Ukraine has illuminated the UK and other nations' reliance on energy imports.
Oil and gas prices have shot up as countries attempt to end the purchase of oil and gas from Russia, which is one of the world's largest fossil fuel producers.
Speaking in Parliament on Monday, Mr Johnson urged the Opec+ alliance of oil-rich countries - which include the likes of Saudi Arabia, Iran and Iraq - to increase production and bring prices down.
Determined to accelerate progress
A Government spokesman told the Telegraph: "While small modular reactors do not yet exist, ministers are determined to accelerate progress where possible.
"The technology offers exciting opportunities to cut costs and build more quickly, and we have already committed £210m towards the project.
"Rolls-Royce's reactor design is currently being assessed by safety regulators - a critically-important process that must be allowed to run its course."