Great Britain’s grid operator has hired independent investigators to look into accusations that its staff were involved in a cover-up over the power system being at a greater risk of blackouts during the heatwave. The government-owned National Energy System Operator (Neso) will face scrutiny from an external legal firm after a whistleblower claimed control room staff were warned against leaving a paper trail relating to efforts to stabilise the power system during record high temperatures in late June.

The accusations, raised in parliament by Conservative shadow minister Claire Coutinho, include claims that senior bosses were “risking blackouts to protect Neso’s reputation.” Coutinho said, “These whistleblowers are coming to me because they are worried that the grid is becoming increasingly unmanageable and they do not have faith that their concerns are being taken seriously internally.” Industry data shows power grid frequency fell below operational limits as the heat dome curbed renewable energy generation and triggered unplanned outages at gas plants, while demand for air-conditioning surged.

The whistleblower alleged that during this period, senior bosses ordered control room staff to ensure there was no audit trail or records of key decisions made relating to managing fluctuations in the electricity system. In a letter to the UK’s data watchdog, Coutinho said a whistleblower alleged staff were told not to keep permanent records and that Neso’s corporate affairs team attempted to pressure operators to protect the organisation’s reputation. “If true, this is nothing short of a scandal,” Coutinho told parliament.

Neso said in a statement that despite unprecedented conditions, the grid operated securely and frequency and voltage remained within statutory limits. The grid’s frequency slumped below Neso’s operational limits of 49.8Hz - 50.2Hz for most of the period between 17.30 and 18.30 on 23 June, but the lowest recorded frequency was 49.66Hz, still above the statutory lower limit of 49.5Hz. The system operator raised the alarm over electricity supplies twice in the last week of June and is estimated to have paid millions for emergency electricity from gas plants, a leading cause of carbon emissions.

Craig Dyke, a director at Neso, said a “full deep dive” into system operations would be undertaken, adding, “Neso has commissioned an independent investigation into recent allegations around decision-making and record-keeping.” Both reports will be published.