Private power plants could be built to support new internet data centres as new computer centres sap power in central London.

Ten huge "internet hotels" are expected to raise demand for electricity by 20 per cent.

Each of these data centres will cover 50,000 square metres and need enough electricity to power two cities the size of Bristol.

London Electricity said it was confident it will not need to follow a Californian electricity firm and cut power at short notice.