Energy companies are cheaper and cleaner when run by the council

London mayor Sadiq Khan has pledged to follow Nottingham and Bristol in setting up a council energy company - and it could shake up the whole market

Sadiq Khan's pledge to establish a municipal energy company, Energy for Londoners, is one of his most striking mayoral election commitments. London will not be the first authority to set up such a not-for-profit company - Nottingham and Bristol got there first - but it will be the largest, and potentially the most ambitious.

The energy market is notoriously uncompetitive, dominated by the big six utility companies, whose pricing practices have led them to be investigated and criticised by the competition watchdog. Most consumers have little trust in these companies, but are reluctant to switch suppliers for a better deal.