The Co-operative today became the first brand name high street store to be able to offer legal services to its customers, the Ministry of Justice said.
The move, which enables non-lawyers to invest in and own legal businesses for the first time, could "transform the way legal services are delivered", experts have said.
People buying a new home could be able to turn to the same firm for services currently provided separately by estate agents and solicitors, while others could turn to supermarket giants for legal advice.
The Co-operative Legal Service was the first brand name to be given approval under the so-called alternative business structures scheme, along with Lawbridge Solicitors Ltd, a family-run firm in Kent, and John Welch and Stammers, in Oxfordshire.
Justice Minister Jonathan Djanogly said: "This is a huge milestone for UK legal services and the future of alternative business structures.
"ABSs introduce more competition in the market place, delivering competitive pricing, higher standards of product and more choice for the consumer.
"Our UK legal services are unrivalled around the world and these changes will allow them to reach new heights, as solicitors' firms develop new markets, seek external investment and join up with other businesses to offer different products to consumers and provide opportunities for growth."
Eddie Ryan, managing director of Co-operative Legal Services, added it was an "historic occasion... for all customers needing access to legal services in the UK".
"We believe that the presence of The Co-operative's trusted brand and values, together with a combination of first class products and services, will provide customers with greater accessibility to expert legal advice and better value for money," he said.
"We are committed to playing a leading role in this new era by offering straightforward value-for-money expert legal services, backed by an ethos of social responsibility and a level of protection that can be provided by a diverse, multibillion-pound organisation."
The Co-op, which was issued its licence by the Solicitors Regulation Authority, has said it plans to tackle the "big issues" that many members of the public have with the legal profession.
While established law firms are often seen as professional, having gravitas and good training, they were also often seen as unapproachable, speaking in a language foreign to members of the public and expensive, because it can be unclear how much a service is going to cost at the outset, the firm has said.
But the move will fuel concerns that local law firms could disappear in the same way as corner shops have been overtaken by the supermarket giants.