The UK’s so-called “big six” energy suppliers –  British Gas, E.ON, SSE, EDF Energy, npower and  Scottish Power – have seen their market share fall to about 70 per cent of consumers, down from 75 per cent last year.

Ofgem’s State of the Market report said the big six’s profits have fallen by a combined 35 per cent since last year, as households switched to smaller firms.

Peter Earl, head of energy at Compare The Market, said: “If the big six continue to shed customers at this pace then by 2024 they will have less than 50 per cent market share – a scenario that would be a remarkable change in fortune for our largest energy players and demonstrate a fundamental transformation of the UK’s energy market.”

Medium suppliers benefitted the most from record switching rates (just over 20 per cent in June 2019, up from 19 per cent the previous year), which swelled their market share by 7 percentage points in electricity and 5 percentage points in gas to more than 20 per cent of consumers overall.

They also gained customers who were transferred to them under Ofgem’s safety net after a number of smaller suppliers failed and exited the market.

Small suppliers for the first time saw their market share fall to 9 per cent of consumers, down from 10 per cent the year before.

“One of the big takeaways from Ofgem’s flagship annual report is the electrified growth of the medium-sized suppliers, such as Octopus, OVO and Bulb, at the expense of the big six and smaller challenger brands,” said Earl, “Meanwhile, the march of the smaller energy brands seems to have short-circuited, with their market share for electricity declining from 10 per cent to 9 per cent in the last twelve months and remaining static for gas. It is possible that the slew of high-profile supplier failures and market exits – 12 in the space of a year – has dampened consumer enthusiasm for switching to a smaller energy provider.”

During the past year, when shopping around for new deals, more consumers turned to price comparison websites (49 per cent), ‘auto-scanning’ notifications (8 per cent) and auto-switching (2 per cent).

Meanwhile, the number of consumers who said they’d never switched suppliers fell to 29 per cent – down from 34 per cent in 2018.

Mark Todd, co-founder of energyhelpline, said: “Ofgem’s State of the Market report shows that record numbers of Brits are switching energy suppliers but still there’s far too much suffering with millions overpaying and thousands dying in cold homes each year.

“Among the shocking statistics unveiled are that more than half of households remain on overpriced standard tariffs wasting £3bn a year, millions live in fuel poverty and, tragically, 16,500 winter deaths last year were linked to cold homes. This is far too high a number for a wealthy developed economy.

“If more seniors could be encouraged to move to cheaper tariffs and claim their winter fuel allowance, the winter death numbers could come down significantly. We urge Ofgem to treat this as the silent crisis it is and take all action it can to alleviate the suffering.”