BIG Six energy firms are charging loyal customers over £300 a year more than new ones.
And the gap between the so-called standard rate that most families are on and the “teaser” rate to entice new customers is getting worse.
The Sun last year revealed seven in ten families were stuck on higher tariffs while new customers were offered cheaper deals.
New research by green power firm Bulb Energy shows in some areas nPower now charges existing customers £328 more than new ones — a 38 per cent surcharge.
In November the gap was £257 or 31 per cent.
Bulb Energy co-founder Hayden Wood said: “It’s most frustrating that this practice seems to be getting worse.”