That means Octopus Energy will sell energy services to consumers under the M&S Energy brand – or what is called a ‘white label’ agreement.
It follows the announcement of Big Six supplier SSE and M&S Energy ending their partnership in September.
M&S Energy will offer 100% green energy to customers as Octopus Energy claims to be one of the UK’s largest investor in solar farms.
Jonathan Hazeldine, Head of M&S Energy said: “Octopus’ value of responsible and transparent pricing and digital-first customer service mirror our ambitions for the business. Together, we can challenge the traditional energy market and bring green energy to millions of households at a competitive and fair price.”