Scottish Power is increasing gas and electricity prices of 5.5% for almost a million of its customers.
The measure, which will enter into force on the 1 of June, you will see typical standard dual fuel bills direct debt of the customers to rise by £63 a year to £1,211.
Those who pay quarterly will see an average increase of £85.
Scottish Power, said that the price change could apply to around a third of its customers, or 960,000 households.
Neil Clitheroe, chief executive of Scottish Power’s retail division, said the increase in the standard variable prices “reflecting the increase in wholesale energy costs, compulsory and non-energy costs”.
He added: “we will be in touch with all customers affected by the change of price to give them the opportunity to move to a fixed price of alternative rate and avoid the increase of this.”
Scottish Power is the third largest energy firm to announce price increases this year.
Earlier this month, EDF Energy said it was raising its electricity prices by 2.7%, days after British Gas raised the price of 4.1 million of its customers.