The Government has launched an investigation into how National Grid allowed the biggest power cut in a decade which plunged the country’s road and rail networks into chaos.

Announcing the inquiry last night, Andrea Leadsom, the energy secretary, also ordered National Grid to tell Ofgem, the energy watchdog, how the failure of a gas-fired power station and a wind farm left nearly one million homes and businesses without power.

“Yesterday’s power outages caused enormous disruption - National Grid must urgently review and report to Ofgem,” she said.

She added the Energy Emergencies Executive Committee, the Government body responsible for ensuring a stable power supply, would “consider the incident”.

The power outage on Friday now means around one million people could be entitled to compensation after losing their electricity supply.