Sainsbury’s share price fell 7% yesterday amid fears that the regulator could put a stop to its plans to merge with Asda.

The two big four grocers have appealed to the Competition Appeal Tribunal for a judicial review of the Competition and Markets Authority’s investigation into their proposed merger.

The grocery giants are requesting a review of the timetable and process of the CMA’s ‘phase two’ investigation as they believe “the current timetable does not give the parties or the CMA sufficient time to provide and consider all the evidence given the unprecedented scale and complexity of the case”.

The CMA has delayed the publication of its initial findings from early January to early February but said the delay was unrelated to the legal proceedings and that its final deadline remained March 5, 2019.

The move has spooked investors, who fear that the landmark merger with Asda may not go through.

The pair shocked the market earlier this year when it was revealed that they planned to merge to create the UK’s biggest grocer: a united Sainsbury’s Asda would outstrip Tesco’s market share.

Rivals including Morrisons, Waitrose and Lidl have warned against the merger. The CMA is conducting an in-depth probe into the deal and the impact it could have on competition.

Sainsbury’s and Asda have argued the merger will “unlock significant cost savings, a large proportion of which will be passed directly on to customers through lower prices”.