Marks & Spencer will be relegated from London's FTSE 100 index for the first time since the inception of the blue-chip index in 1984, according to Reuters calculations based on Tuesday's closing prices.

The 135-year old retailer's shares were valued at 3.7 billion pounds, making it the 115th most valuable stock among London-listed companies, according to closing data.

FTSE Russell, London Stock Exchange-owned index provider, requires companies to be ranked 110 or higher to be a part of the FTSE 100 index.

The final FTSE 100 review will be based on closing prices on Tuesday, with the results announced after the end of trading on Wednesday. It will go into effect on Sept. 23.

FTSE Russell said on Monday that high-street icon was among the likely companies to be excluded from the UK blue-chip index based on Friday's closing prices.