Marks & Spencer must change its strategy in a “fundamental way”, close its Simply Food stores and open a new chain to attract young consumers if it is to thrive, a leading retail analyst has said.

According to Tony Shiret of Credit Suisse, Marks & Spencer has made “no financial progress” since executive chairman Sir Stuart Rose stepped in almost five years ago.

In a 108-page note, Shiret also raised the prospect of the need for a change in management if profits continue to slide.

Shiret said: "Even before the current rapid deterioration of profitability the company had made no financial progress outside of the£320m of largely supplier-funded cost savings initiated in 2004 and around£150m resulting from changes in accounting assumptions."

Shiret said the retailer’s customer base is far too old and it has been ignoring younger shoppers.

He said: “Of greater concern has been the failure to address and reverse the company’s drift towards a much older customer base … No business can have a long-term future with this type of demographic profile in our view.”

He added that M&S should establish a “more relevant young chain” in its small stores, while serving its older customers in its larger stores.

Credit Suisse expects M&S’s pre-tax profit to fall for the next three years. It forecasts that by 2011, it will come in at£325m, from£1bn last year.