LONDON, May 11 (Xinhua) -- Britain's major gas and electricity supplier Npower is to raise energy bills by an average of 64 pounds (86.72 U.S. dollars) a year for a million customers, representing an average hike of 5.3 percent, the German-owned company announced Friday.

The dual fuel price hike comes into effect on June 17 and follows earlier rises announced last month by its "big six" rivals, the company said.

The overall increase is based on an average rise of 4.4 percent on gas and 6.2 percent on electricity.

The government said that it had been forced to make the move by higher wholesale energy costs and cost burdens imposed by the British government.

British Gas is increasing prices by 5.5 percent from May 29, while Scottish Power is raising prices by 5.5 percent on June 1.

The company, owned by Germany's Innogy, said that more than 60 percent of its customers, such as those on fixed tariffs or using prepayment meters, would not be affected by the change.

Price comparison service Uswitch said the hike makes Npower's standard tariff the most expensive on offer from the big six energy providers.

"The average 64-pound rise is the equivalent of almost three weeks spending on energy," said Claire Osborne, Uswitch energy expert. "With the recent wholesale cost increases, now is the time to switch and lock in a fixed deal to protect yourself against future price rises."

"Energy suppliers haven't been afraid to increase prices in spite of the threat of an energy price cap -- perhaps because they're confident that customers will mistakenly think a cap protects them, so they won't switch once it's in place," Osborne said.