Centrica has extended its gas supply contract with Norwegian energy firm Statoil.
The volume of gas will increase by a further 2.3 billion cubic meters (bcm) to 7.3bcm a year.
This is an extension of a 10-year contract signed by the companies in 2011 for 5bcm of gas a year to be delivered to the UK from October 2015.
The British Gas owner has also signed a separate gas supply contract with Russian energy giant Gazprom Marketing & Trading Limited. This will increase gas delivery by 4.16bcm – a total of 29.1bcm a year.
Britain needs around 70bcm of natural gas every year and the UK now needs to import more than half of this, according to Centrica.
The long term supply agreements with Statoil and Gazprom will meet the gas needs of nine million British homes every year.