The CMA has slammed Morrisons for having the “poorest compliance record” it has so far seen with rules against land deals that prevent rivals from opening nearby.
The supermarket was found to have 55 land deals that breached the rules.
The CMA said 14 of the deals had already ended and Morrisons had agreed to address the remaining 41.
M&S was found to have 10 land deals in breach of the rules, five of which had already ended, with the retailer agreeing to address the other five.
Morrisons and M&S’s breaches have come to light in the latest outcome of action launched by the CMA in 2020, after it found Tesco had breached the rules 23 times. The authority wrote to the other six retailers covered by the rules asking them to show their land agreements were not in breach.
In May this year, 18 breaches by Sainsbury’s were exposed, as well as 14 by Asda.
The CMA action also brought to light seven breaches by Waitrose in 2022.
“At a time when the weekly shop is a source of financial pressure for many families, it’s crucial that competition between supermarkets is working well to help people get the best deals they can,” said Adam Land, senior director of remedies business & financial analysis at the CMA.
“These restrictive agreements by our leading retailers are unlawful. There can be no excuses made for non-compliance with an order made in 2010, especially when we know the positive impact for shoppers of new stores on the high street.
“Our continued crackdown on these unlawful restrictions is part of our wider action to tackle the cost of living and ensure that people benefit from more competition and choice.”
An M&S spokesperson said: “We are disappointed that having worked closely with the CMA over the past three years, it has highlighted 10 breaches, five of which are historic and expired.
“These have made no practical difference to the activity of our competitors or our tenants and did not adversely affect competition.
“We are remedying these immediately, continuing to work with the CMA, and have introduced tighter internal governance and compulsory training to prevent it happening again.”
A Morrisons spokesperson said: “We co-operated fully with the investigation and accept its findings. We now plan to rectify the outstanding breaches quickly.”
The CMA has separately been reviewing pricing competition in the groceries sector, and last week published an update calling out some branded suppliers for pushing up prices during the cost of living crisis by more than their costs increased.”
That followed an update on a probe into retail competition in May, which cleared supermarkets of profiteering claims.