It would be “a tragedy” if John Lewis changed its ownership model, a former boss has said.

Reports last week suggested the company is considering ending its 100% staff-owned structure, with the partnership’s chairwoman, Sharon White, exploring plans to sell a minority stake in the business to raise cash.

West Midlands Mayor Andy Street, who was managing director of the retailer until 2016, acknowledged the company’s financial difficulties, but urged the leadership to think about what makes it “special”.

He told BBC One’s Sunday With Laura Kuenssberg: “It would be a tragedy if that occurred because I think John Lewis goes a bit beyond a shop.

“You can buy the same television in other places is the truth, but John Lewis was about actually a way of doing business, actually showing the market there was a better way almost, and in fact that’s now potentially under threat.

“So I would urge the leadership of John Lewis to think about what’s really at the heart of it, what makes it special, and hold on to that.

“You have to address the underlying point. This was ever the case in the John Lewis model over 150 years – if you can’t go to the equity markets you have to trade your way through it.

“Some of the best retailers at the moment – Next, Primark, Selfridges – are proving physical retail can still do that, and that’s really the challenge to John Lewis and Waitrose.”

It came as former minister Gareth Thomas said John Lewis could be helped to remain staff-owned by a proposed law to be tabled in Parliament.

The Harrow West Labour MP plans to introduce the Co-operatives (Permanent Shares) Bill on Wednesday, aimed at helping companies with the same ownership structure as John Lewis to remain “owned firmly by British people”.

The chairman of the Mutuals All-Party Parliamentary Group told the PA news agency: “It is the route to help John Lewis stay completely employee-owned.

“At the same time, it would potentially help co-operatives and mutuals access significant capital to invest in their businesses, expand the services they offer, and more.

“It will allow co-operatives and mutuals to issue shares that would not change the governance structure of their business.

“The return for the investor is similar to a traditional loan or a bond in that way.

“There is a dividend or interest return, but crucially what you don’t give up is significant ownership rights.”

He added: “Basically it is rocket fuel for the co-operative and mutual sector.

“It would help to provide significant capital investment for them over time without risking fundamental changes in the way their business operates.”

A John Lewis Group spokesman said: “We’ve always said we would seek partnerships to help fund our transformation and exciting growth plans.

“We’ve done this with Ocado in the past and now with abrdn.

“Our partners, who own the business, will be the first to hear about any developments.”