The 5.5 per cent increase will affect both energy and gas bills and affect customers on the standard variable tariff (SVT).
The price increases will see a typical dual fuel customer annual bill rise by £60 to £1,161 – £30 for gas and £30 for electricity.
The price hike will come into force from 29 May 2018.
In a statement released by Centrica, the parent organisation of British Gas, credited the price increase to rising wholesale and policy costs which they said is beyond their control.
Mark Hodges, CEO, Centrica Consumer said: “We fully understand that any price increase adds extra pressure on customers’ household bills.
“We stopped selling the SVT, which has no end date, on 31 March so it’s no longer available to new customers. We are also encouraging our existing customers on this tariff to choose one of our new fixed-term deals. And by the end of 2018 we hope over 1 million more customers will have chosen to move onto one of these alternative deals.”
The price increase will not affect the 3.7 million customers on fixed-term contracts, prepayment meters and vulnerable customers.