Morrisons is set to fall out of the FTSE 100 after seeing its share price fall 11% over the past month alone.
The supermarket has been one of the worst affected by the industry price war as smaller rivals like Aldi, Lidl and Waitrose continue to gain popularity.
The London Stock Exchange Group, which reviews the companies on the index quarterly, said Morrisons is likely to be demoted to the FTSE 250, alongside security firm G4S.
The final decision is based on share prices on Tuesday night, which according to analysis by the Guardian, puts Morrisons out of the FTSE 100.
Last month, the supermarket reported a 2.6% fall in like-for-like sales in the three months to November, even more than the 2.4% decline seen in the previous quarter. Morrisons chief executive David Potts is expecting a stronger Christmas period in 2015 than last year, when underlying sales dropped 3.1%.
“Our internal forecasts are promising something better, but in retail you have to go out there and do the job,” he said.