Sainsbury’s Energy, which has a white label agreement with British Gas, will transfer all its customers to the big six provider in April.
The supermarket chain, which has partnered with British Gas since 2011, says it has made the decision to “switch energy providers”.
Those customers with Sainsbury’s will continue to be supplied by British Gas under the same terms and conditions.
A spokesperson for Sainsbury’s said: “We regularly review our partnerships based on a range of factors.
“We can confirm we have made the decision to switch energy providers and will continue to work with British Gas until spring.”
There is currently no indication of which energy provider Sainsbury’s will switch to, or how the business will operate after transferring its customers.
A spokesperson for Centrica, the parent company of British Gas, said: “We can confirm the partnership between Sainsbury’s and British Gas is coming to an end.
“We have enjoyed a successful partnership with Sainsbury’s since 2011 and we will be writing to Sainsbury’s Energy customers to reassure them they will continue to be supplied by British Gas under the same terms and conditions and they will now be able to join the British Gas Rewards loyalty programme.”
In July last year Marks and Spencer Energy and SSE announced they were ending their partnership of nine years.
Marks and Spencer later announced it was partnering with Octopus Energy.