National Grid's headquarters are lit up "like a Christmas tree" - 24 hours after the firm warned of electricity shortages this winter.
Bosses told Britons supply will be at a seven-year low due to generator closures and breakdowns - and said spare capacity will be at just 4%.
But hours after the grim warning, a photographer captured lights shining brightly from empty offices and car parks at their head office.
The snaps were taken at 7.30pm - when the majority of workers at the Warwick HQ had gone home for the day.
National Grid insists it has contingency plans in place to manage supply - including paying big firms to switch off on cold winter evenings.
But judging by these damning photographs, it appears they are not heeding their own advice.
James Robinson, 42, who works nearby, said: "It's ridiculous that this huge building is lit up like a Christmas tree.
"When we leave our office we make sure the lights are switched off but these people should definitely know better.
"It reeks of hypocrisy - it's just not on."
As well as paying factories to turn off machines, energy firms could also be bribed by the National Grid to switch on back-up power stations.
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Jeremy Nicholson, from the Energy Intensive Users Group, which represents major manufacturers, said: "There was an obsession early on with being the greenest government ever.
"We all want to see cleaner energy - who wouldn't - but it is becoming increasingly obvious that we want clean energy at a price we can afford.
"We urgently need to be building new gas fired power stations and get cracking on the nuclear programme."
National Grid and politicians insist there is no chance of homes completely losing power.
Energy Secretary Ed Davey saying: "There will be no blackouts. Period."