More than £863 million of taxpayer’s cash is being handed over by local authorities to the Big Six energy providers or oil giants as councils fail to switch to smaller providers, research has found.

Nine out of 10 local authorities in Britain are supplied by one of the major UK energy or oil firms, according to the results of a Freedom of Interest (FOI) request by smaller supplier Bulb.

This comes despite a raft of council leaders openly encouraging residents to switch to challenger suppliers to save cash and be more environmentally-friendly.

In contrast, 20% of households have switched to a smaller energy firm.

Citizens UK urged councils to shop around to find the best deal for taxpayers.

Caitlin Burbridge, a community organiser with Citizens UK, said: “Councils have a responsibility to seek the best value for money for their residents, and spending on energy should be no different.

“With many smaller suppliers offering cheaper tariffs, and often green energy, councils should look to shop around rather than continue to stick with the Big Six.”

Responses from 273 out of 408 local authorities in the UK to the FOI discovered councils were paying over £863 million a year to the major providers, with mammoth differences in the amount forked out for energy bills.

The study found 243 of the 273 authorities which responded use a large supplier, including 92 with Npower, 45 using EDF Energy, 36 opting for Total Gas & Power and 49 using a mixture of large providers.

It also showed residents paying as much as £83.32 on average a year in Milton Keynes for the unitary authority’s energy, versus just £4.99 in Portsmouth, although these figures are also dependent on the number of residential properties and other factors.

In Orkney Islands in Scotland, households are forking out £165.46 a year for council energy against £44.48 per household in Renfrewshire.