Household energy bills have climbed at almost twice the rate of inflation despite booming competition bringing an end to the dominance of the “Big Six” providers.

Families paid an average of £571 a year for electricity and gas in 1998, compared to £1,447 in 2018, according to data from industry analysts Cornwall Insight. This equates to an annual increase of 5pc a year, while inflation over the same period was 2.8pc.

This is despite the number of companies supplying energy ballooning from eight in 2007 to 61 last year.

In 2013, then prime minister David Cameron bemoaned the lack of competition and made it easier to set up an energy firm in a bid to turn the “Big Six into the Big 60”. Until then, the six biggest providers – British Gas, SSE, EDF, Npower, E.On and Scottish Power – supplied more than 97pc of households. Amid rising competition, this dominance has collapsed to 70pc.

The heyday of the Big Six now looks to be all but over, after the competition regulator signed off both the takeover by E.On of Npower and the takeover of SSE by mid-sized supplier Ovo, which will become the second largest energy firm.

A side effect of the rapid expansion of the market has been the number of suppliers that have collapsed, leaving customers in the lurch. Fifteen energy firms have gone bust in the past two years, affecting more than a million customers.