The night the lights nearly went out: Whistleblowers claim Britain was on brink of shutting down on June 23 during heatwave

By CLAIRE ELLICOTT, WHITEHALL EDITOR Published: 23:41, 15 July 2026 | Updated: 23:54, 15 July 2026 Britain came close to blackouts during last month's heatwave – but energy bosses tried to hide it, whistleblowers have claimed. Shadow energy secretary Claire Coutinho told MPs that operators claimed that on June 23, the grid failed to meet necessary standards as temperatures reached 34C. She added that they claimed that the Neso (National Energy Systems Operator) corporate affairs team had tried to cover up the crisis. But energy minister Michael Shanks insisted that electricity supplies were maintained and that no customers lost power. However, he said that Neso – a government body set up by Energy Secretary Ed Miliband – had now ordered an independent investigation into the claims against it. In an urgent question, Ms Coutinho told MPs that whistleblowers had warned that the country was close to blackouts. 'I've been approached by multiple whistleblowers within our grid operator,' she said. 'The allegations are that first, on the 23rd of June, the operator failed to meet the grid security standards put in place to prevent blackouts. Whistleblowers claim Britain was on brink of shutting down on June 23 during heatwave  'Second, that the corporate affairs team interfered with operational decisions. 'That is not something that the minister denied - putting the reputation of the operator above security of supply. 'And third, that operational decisions are being recorded in live documents with no audit trail. Again, something the minister did not deny.' She previously accused grid bosses of 'risking blackouts to protect Neso's reputation'. In the run-up to the incident in June, Neso issued an emergency margin call - a request to generators to increase supplies - after forecasting a shortfall. Government departments were warned about the risk of power cuts. Mr Shanks said that there had been no blackouts last month and said that there was no kind of 'emergency situation'. 'Electricity supplies were maintained throughout the June heatwave. No customer demand was disconnected,' he said. 'Statutory frequency limits were maintained throughout the whole event, and the largest credible loss that could have occurred was also covered.' He added that at no point did the country 'come close to breaching' the 'margin' – the buffer above peak demand. 'It did not indicate any kind of emergency situation. Demand was met, and those are the facts,' he added. He later added that although the electricity demand had been met, 'I don't for a second doubt that it was difficult on some of those days, as it was across all of Europe.' He also said that Neso had instructed a legal firm to conduct an independent investigation into the claims of the whistleblowers. The report will be delivered to the operator and to regulator Ofgem 'in the coming weeks', Mr Shanks said. But Ms Coutinho dismissed this as a 'sham' because there was no guarantee that workers would be granted anonymity. Her fellow Tory MP Julian Lewis questioned whether the review would be independent because Neso was paying for a law firm to investigate. Meanwhile, Bill Esterson, the Labour chair of the energy committee, said a director at Neso had told him it was 'not plausible' that corporate staff had taken decisions in the control room. Neso issued its third electricity margin notice of the year last week. They are the first such notices to be put out in summer and it has issued only two others - both in January last year - since it took charge in October 2024. Extreme heat puts pressure on the electricity system by making processes less efficient, including generation from nuclear power plants, gas stations and water-cooling systems. Britain has not suffered a major blackout since 2019 when the Little Barford gas-fired power station in Bedfordshire and the Hornsea windfarm in the North Sea failed at the same time, causing large parts of the grid to automatically shut down. An unprecedented blackout left Spain and Portugal without electricity for several hours last year, leading to questions about the reliability of the electricity supplies in times of stress.