Britain was on brink of shutting down last month as energy bosses tried to hide potential blackout disaster, whistleblowers claim

Shadow Energy Secretary Claire Coutinho informed Parliament that she had been contacted by multiple insiders from the National Energy System Operator (Neso) with serious concerns about events on June 23, when temperatures soared to 34C.

The whistleblowers claimed that on that date, the grid operator “failed to meet the grid security standards put in place to prevent blackouts”.

Departments across Whitehall were reportedly warned about the possibility of power cuts in the lead-up to the incident, after Neso issued an emergency margin call requesting generators to boost supplies following a forecast shortfall.

Beyond the failure to maintain security standards, she told MPs that Neso’s corporate affairs team had “interfered with operational decisions”, prioritising the organisation’s reputation over security of supply.

The third allegation concerned record-keeping practices, with whistleblowers claiming that “operational decisions were being recorded in live documents with no audit trail”.

Ms Coutinho accused grid bosses of “risking blackouts to protect Neso’s reputation” and suggested the corporate affairs team had attempted to cover up the crisis.

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Energy minister Michael Shanks hit back, firmly rejecting suggestions that blackouts had been imminent, insisting the national grid had remained stable throughout the period of unprecedented heat.

He told MPs: “No customers were impacted by tight electricity margins and Neso had a number of tools available to them to ensure our energy security.”

Mr Shanks confirmed that electricity demand had been met on every day in question, with statutory frequency limits maintained throughout.

He stated that at no point did the country “come close to breaching” the safety margin above peak demand.

The minister accused Ms Coutinho of “conflating” whistleblower concerns with blackout risks, calling it “absolutely irresponsible” to suggest the energy system had been in jeopardy.

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He acknowledged the period had been challenging, as it was across Europe, but maintained there was no “emergency situation”.

Neso has commissioned an external legal firm to carry out an independent inquiry into the allegations, with findings due to be delivered to the board’s head of risk and controls and to regulator Ofgem within weeks.

However, Ms Coutinho dismissed the investigation as a “complete sham”, arguing it would not examine whether security standards were breached on 23 June and offered no guarantee of anonymity for control room staff wishing to come forward.

She also revealed that Neso’s chief executive had described the allegations as false during an all-staff call on Monday, while senior management accused the whistleblowers of having “let them down”.

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“The whistleblowers who put the national interest over their own careers should be celebrated for their courage and their integrity, not denigrated,” Ms Coutinho declared.

The electricity margin notices issued by Neso during the heatwave were the first such alerts to be released during summer months.

Since taking charge in October 2024, the operator had only previously issued two notices, both in January last year.

Periods of extreme heat place significant strain on power generation, reducing efficiency at nuclear facilities, gas-fired stations and water-cooling systems.

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The UK’s most recent major blackout occurred in 2019, when the Little Barford gas power station in Bedfordshire and the Hornsea offshore wind farm failed simultaneously.

This caused automatic shutdowns across large sections of the network, causing chaos for commuters, halting many major rail networks and knocking out traffic lights.