A record 1.7 million complaints were lodged against the Big Six energy companies in the first four months this year, according to a consumer body.

The figure is claimed to be the highest in a single quarter since 2012 and is up from 1.48 million in the same period last year – a 15% rise.

Supplier npower faced the most complaints, with an average of 83 objections per 1,000 customers, a rise of 70% year-on-year. That was mainly due to the company switching to a new billing system last year that resulted in some customers’ direct debits being cancelled and others receiving no bill at all.

Among the rest of the Big Six, EDF Energy recorded 46 complaints per 1,000 customers, E.ON 33, British Gas 31, SSE 28 and ScottishPower 14.

Which? Executive Director Richard Lloyd said: “Yet again millions of customers are being let down by poor service from the Big Six energy companies. This has to change.

“If they want to improve the low level of consumer trust in the energy market, suppliers must up their game now, rather than wait for the results of a competition review.”

The trade body for the energy industry, however, insisted “most customers are happy with their energy providers” but agreed that “sometimes things can go wrong”.

Energy UK said: “Energy companies work very hard to resolve problems and most complaints are fixed within a few working days with no more than a phone call.

“Our members put customer service at the heart of what they do. The companies are working hard to be as transparent and straight forward as possible… No one wants to see complaints rise but the industry uses this information to improve its service.”

Earlier this week, regulator Ofgem proposed new rules that will allow consumers to switch suppliers in just three days, cut down from the five weeks it takes at the moment.