Last week, the partnership, which owns John Lewis department stores and the upmarket Waitrose supermarket chain, confirmed it was considering selling a minority stake in the business to outside investors to fund investment.

The partnership has warned it will have to cut staff numbers and scrap any bonus this year after its customers reduced spending, prompting its annual loss to balloon to 234 million pounds ($286 million).

"Somehow, in recent years, you've let go of the soul," wrote Portas, known as the "Queen of Shops" due to her efforts to save the UK high street.

She accused John Lewis of "chasing the new. New systems, new people, new identity...new owners. But here's the thing: that's not what we really want from John Lewis".

John Lewis' Chairman Sharon White wrote back to Portas insisting she would ensure the partnership not only survives, but thrives.

"Our Partners (employees) who own the business are our greatest asset and our ownership of the Partnership will remain," she said, but added: "We've always been open to new partnerships with investors or like-minded companies to share our growth."

($1 = 0.8177 pounds)

(Reporting by James Davey; editing by Jason Neely)