A total of 5.5 million customers switched in 2017 – up from 4.8 million in 2016.
There are now almost 60 energy suppliers in Britain – although some 85% of the gas and electricity market is dominated by the Big Six providers.
The data comes as the Big Six are under pressure to reduce bills and as regulator OFGEM prepares to impose a price cap on the most widely used tariffs.
The data does not show which companies lost or gained the most customers, but Centrica – which owns the British and Scottish Gas brands – yesterday revealed that it lost more than 800,000 customers in the four-month period ending November last year.
Steven Day, Co-Founder of Pure Plant, an app-only energy provider, commented: “This is seismic. No other industry is seeing such dramatic consumer change.
“We’re witnessing a great acceleration away from the Big Six to the better, cheaper benefits of the independents.
“Our own research revealed half of customers with the Big Six are now considering switching to cheaper, cleaner companies. People are speaking with their wallets and choosing affordable energy independent firms.
“Companies like Pure Planet are beating the Big Six hands down by cutting emissions, lowering prices and providing a digital first service which suits people’s modern lives.
“This really is a watershed moment for the energy industry in this country.”