The signed agreement will see the Norwegian energy firm deliver an additional one billion cubic metres of gas supplies to the UK for each of the next three winters.
That is predicted to be a sufficient amount to heat an additional 4.5 million homes.
Last week, the British Gas owner filed an application to the North Sea energy regulator to reopen the UK’s largest gas storage facility.
Business and Energy Secretary Kwasi Kwarteng said: “With Russia’s criminal invasion of Ukraine, it is more important than ever that we source more of the gas we need domestically, but also from safe and reliable import partners while we transition.
“We cannot, and will not, turn off the taps overnight.”
Chris O’Shea, Centrica Group Chief Executive, said: “This agreement is good news for our customers and the country. At a time when energy security is paramount, I’m pleased that we are able to do our bit to ease the pressure and provide some more certainty ahead of what may be a difficult winter.”