Grocers, banks and other high street retailers will all be able to offer legal services to customers from today.
The move, which enables non-lawyers to invest in and own legal businesses for the first time, will not necessarily be a "big bang moment" with radical changes overnight, but could "transform the way legal services are delivered", experts 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 be able to turn to supermarket giants for legal advice.
Despite frequently being dubbed "Tesco Law", the supermarket giant has said it has "no current plans to offer legal services".
But the Co-operative was among the first of the brand name stores to say it was interested in offering legal services to its customers, adding it was seeking to get the necessary registration as soon as possible.
Jonathan Gulliford, sales and marketing director for the Co-operative Legal Services, said most of its customers were not used to dealing with solicitors, adding it was "not something they want to be doing and on the whole they don't like doing it".
"We want to get in to help our members and to do the work for them," he said.
The Co-op plans to tackle the "big issues" that many members of the public have with the legal profession, he said.
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.
"We want to combine the positive qualities but deliver the services in a way that customers want," Mr Gulliford said.
"We will always give an up-front fixed fee price before we undertake any work."
He added that the "world is changing" and people also wanted to access legal services online and remotely, without having to take a day off work.
Mr Gulliford also denied that the changes could see local law firms disappear in the same way as corner shops have been overtaken by the supermarket giants.
"Good small firms of solicitors will adapt and people will still want to use them", he said.
"But some businesses will go out of business, those that are not prepared to adapt and wake up to the fact that the anti-competitive rules they've been benefiting from are changing.
"But I can't see anyone crying over that."
Eddie Goldsmith, chairman of The Conveyancing Association, said: "Today isn't necessarily a big bang moment but it could change the face of our legal services as non-lawyers can now invest in and own law firms.
"I don't think we will see a radical change overnight with supermarket law firms popping up but there is an opportunity to transform the way legal services are delivered.
"We know that when making important decisions such as buying a new home, consumers want an easy-to-access quality and trustworthy service and if the big brands can offer this, the consumer should benefit, as long as the quality of advice isn't undermined."
He went on: "For existing high street firms, today's changes could prove very challenging as there may be increased competition.
"But providing legal services isn't the same as selling baked beans. Those currently providing legal services will need to improve the way in which existing services are delivered in order to meet public needs and this can only benefit the consumer."
Justice minister Jonathan Djanogly added: "This is a landmark day for the UK legal industry.
"Our legal services are already rated among the best in the world, used by millions of people around the globe as well as in the UK, and these changes will set them up to move to new heights.
"They will enable firms to set up multi-disciplinary practices and provide opportunities for growth.
"Potential customers will find legal services become more accessible, more efficient and more competitive."