Nearly 1m households will see their energy bills jump by £63 a year after Scottish Power became the fourth of the big six suppliers to raise their prices.

The 5.5% increase on a typical dual fuel bill for 960,000 customers is the same percentage rise as British Gas announced earlier this month and higher than ones from E.ON and EDF. The increase takes affect on 1 June and will affect about a third of Scottish Power’s customers.

SSE and npower are the only two other big energy firms yet to declare a price rise, before the government’s planned cap on standard tariffs later this year.

Scottish Power, which is owned by the Spanish energy giant Iberdrola, cited the same reasons as other big suppliers: rising wholesale cost, government schemes levied on energy bills and the rollout of smart meters.

EDF Energy announced a 1.4% increase for more than 1 million customers earlier this month. The French state-owned supplier will raise dual fuel bills for 1.3 million customers – nearly 40% of EDF’s total – on standard variable tariffs, increasing the average bill by £16 to £1,158.

E.ON was the first of the major energy firms to put up prices this year, announcing in March that about 1m households would face higher gas and electricity bills from 19 April.