Britons could face being plunged into darkness with nationwide blackouts after the National Grid changed rules to help hit the Government’s green targets.

The National Energy System Operator (Neso) is set to operate the grid with reduced levels of ‘inertia’, which behaves like shock absorbers to keep spinning parts moving in the event of a power plant failure.

The change to the new lower minimum inertia threshold will save consumers £96million a year, the state-owned body said.

But electricity firms warned the move could put the UK at a greater risk of blackouts, and a whistleblower described it as ‘truly insane risk-taking’ and a ‘massive gamble’.

Neso said inertia is a by-product of coal and gas-fired generators, provided by heavy turbines used by fossil fuels and nuclear power. It means the turbines continue spinning even if there is a problem. 

However, renewables such as wind and solar do not provide inertia, so the body has been exploring ways to generate inertia in other ways as it hurtles towards a zero-carbon grid.

It said the ‘world-first initiative’ will use either new assets or existing infrastructure that has been modified to draw energy from the grid to power their turbines and create inertia, rather than being a by-product of producing electricity.

Neso has not confirmed the timescale for the change, but insisted there would be ‘no tangible increase’ in risk to blackouts, as it can use rapid-response batteries to respond to supply shocks. 

Pylons stand in fields in Linford, Essex

The operator of Britain’s biggest power plant, Drax, warned that any cost savings would be ‘immaterial’ compared to the potential fallout from a system failure caused by a lack of inertia.

EDF, which operates Britain’s nuclear reactors also warned that potential ‘country-wide or regional blackouts’ would create an economic loss greater than any possible savings made.

The operator urged caution in reducing minimum inertia levels.

A spokesman said: ‘Maintaining grid stability is becoming more challenging as the system becomes more diverse. 

Nuclear power plays a key role in system stability, including the provision of inertia, and new projects will play a vital role in future alongside further growth in grid scale batteries. Further reducing minimum inertia levels at this point in the transition is premature.’ 

Control room engineers previously told The Mail on Sunday that bosses in charge of the creaking national energy grid are putting lives in danger because they refuse to admit the system is on the brink of collapse.

Whistleblowers said that safety breaches are routine, and a catastrophic blackout is an ‘engineering certainty’.

Accusing bosses of a cover-up, concerned insiders say they spent two years warning executives at the Neso and regulator Ofgem that the rush to Net Zero means they have ‘lost control of the system’. Yet no action was taken.

Last month, Ofgem ordered an investigation after leaked documents revealed the network came close to shutting down on June 23 thanks to a shortage of wind and solar energy.

But sources told the MoS that the true scale of the problem is far worse and the electricity grid has been out of control since Labour came to power and accelerated the push for ‘clean’ energy. 

They warned that thousands of new wind farms, solar farms and battery storage units are destabilising the network.

Now a group of Neso engineers have appealed to the public and Ofgem to help expose the truth.

‘We the engineers have asked Ofgem to investigate and ensure the system is safe for two years now. That is simply done by asking for proof that Neso can always work out how much energy is required. And they won’t do that and they won’t investigate. So we have told the world.

‘June 23 was simply another day. We don’t have control of the system. We have tried our best. It’s now over to the public and the regulator. Please help.’ 

Last year’s 16-hour power cut in Spain and Portugal – widely blamed on problems caused by vast solar farms – led to eight deaths directly but is likely to have caused 165 more in the following two days.

One Neso whistleblower told the MoS: ‘It’s getting worse day by day. We’re now flying blind with the plane on fire. It’s not a matter of ‘if’ there’s going to be a major blackout, it’s an engineering certainty.

‘If we overload parts of the system, that means things will catch fire or explode. We’d have cables crashing to the floor, perhaps over motorways, then arcing over, spraying flames, before they hit the floor.’

A spokesman for Neso told The Times: ‘The secure operation of Great Britain’s electricity system is Neso’s highest priority. The analysis shows these proposals will maintain system security while delivering significant savings for consumers.’

The Department for Energy Security and Net Zero said: ‘The UK has one of the most reliable electricity systems in the world – in its 75-year history, there has never been a complete grid shutdown.

‘We are very confident in our security of supply arrangements, and that Neso have the tools they need to manage the system.’