The Competition and Markets Authority (CMA) has rejected a claim by Sainsbury’s and Asda that they need more time to process all the evidence generated by the inquiry into their proposed merger.

The CMA responded after the retailers applied to the Competition Appeal Tribunal for a judicial review of the CMA’s phase two investigation into their proposed merger.

The application requests a review of the timetable and process, because they claim it gives neither them, nor the CMA, sufficient time to provide and consider all the evidence given the unprecedented scale and complexity of the case.

In a statement the two companies said they had engaged constructively with the CMA and made repeated requests for additional time. Specifically, they said they have asked the CMA for an additional 11 working days over the Christmas period to respond to a large amount of material recently provided to them.

However, the CMA responded: “Our first priority in this investigation has, and will continue to be, assessing if shoppers would face higher prices or a lower quality of service as a result of the merger and, if so, to prevent that from happening.

“We began to engage with the companies involved as soon as they announced their intention to merge at the end of April, to make sure they had the opportunity to fully put forward their views. Investigating any merger of this size requires assessing a large volume of material in a short timeframe, and it is not unusual for the companies involved to do this in the timelines we have been working to with Sainsbury’s and Asda. We have done everything we can to aid their consideration of this work, while still ensuring we are able to meet our legally-binding deadline. This includes extending certain administration timelines where appropriate.

“If we gave the companies the extra time they are now asking for, it would put our ability to complete the investigation by the required deadline at very serious risk. As with all of our merger reviews, we construct our timetable to ensure that everyone has the chance to have their say, including customers, the companies involved and suppliers.”

Between them, Sainsbury’s and Asda operate around 630 petrol filling stations with a 17.9% share of the road fuel market.