The National Energy System Operator (Neso), which manages Great Britain's electricity grid, has become embroiled in a political dispute after Conservative shadow energy secretary Claire Coutinho alleged that whistleblowers within the organisation accused senior managers of covering up how badly the power system was strained during June's heatwave. The claims include allegations that control room staff were told to abandon normal record-keeping to avoid an audit trail, and that corporate affairs staff pressured operators into decisions designed to protect Neso's reputation rather than the network's stability. Neso denies the allegations and has appointed law firm Eversheds Sutherland to investigate, but the row has fed into a wider political and cultural battle over Britain's net zero targets and clean energy costs.

The disputed events centre on the last week of June, when a "heat dome" over Europe reduced output from wind turbines, gas plants and French nuclear imports just as demand for air conditioning and refrigeration surged. Neso responded with a series of emergency measures never previously used in summer, and figures show it spent almost £800,000 paying consumers to cut electricity use between mid-April and mid-July. Grid frequency, which Neso aims to hold around 50Hz within a safe range of 49.8Hz to 50.2Hz, came under sustained pressure for nearly an hour on 23 June, dropping to close to its lower operational limit.