This is the first time the company will drop out of the index since it was established 35 years ago.

This removal from the list is another blow for the company, which is already due to close 120 of its stores as part of an overhaul intended to increase profits.

The stock market confirmed the removal of the company from the list by the documentation of M&S closing prices yesterday. The closing prices determine the quarterly reshuffle of the top UK-listed companies.

The official announcement is due to be made today and the changes will take effect on the 23^rd of September.

Also finding themselves removed from the FTSE 100 list are Micro Focus and Direct Line, who will make room for the emergence of Polymetal, Hikma and Meggitt on the list.

It has been almost certain that M&S would be removed from the list following a decline in its share price, orf more than 45% over the last three years. This share price is also at an almost 20 year low. This low follows an extensive and long-running sales slump within its clothing range, this has been amplified by the enduring high street crisis.

Helal Miah, investment research analyst at Share Centre, said: “M&S for many generations has been a stalwart of the UK retail market and a founding member of the FTSE 100. Its relegation will be highly symbolic of the troubles on the UK high street and the challenges the UK retail sector faces as the internet plays an increasingly important role.”

For M&S chairman, Archie Norman, this is the second time a company he controls has left the index. He was also at the helm of ITV when it was relegated.

He said: “When I went to ITV we dropped out of the FTSE 100. The sky didn’t fall in – the business was the same the day after. Companies which narrowly avoided dropping out this time round include Centrica. It was aided by the fact that Micro Focus issued a profit warning last week, making the software giant a prime candidate for demotion.”

Tony Shiret, an analyst at stockbroker Whitman Howard, said: “It is significant (for M&S) in the sense that it is a fairly objective measure of the diminished scale of the company.”

Nick Bubb, an independent retail analyst, said M&S had been in the relegation zone for some time.

He said: “M&S has been declining remorselessly for many years, as a result of weak and arrogant management and stronger, more focused competition [like Primark],” he said. “The problems have mainly been on the clothing side, where M&S tries and fails to be all things to all people in the mid-market.”