Eurotunnel Dover-Calais MyFerryLink service appeal
The competition authority says it is looking to take the legal wrangle over Eurotunnel's cross-Channel ferry service to the Supreme Court.
On Friday, the Court of Appeal ruled the Competition and Markets Authority (CMA) did not have jurisdiction over the purchase of three ferries.
Eurotunnel bought the three ships from SeaFrance in 2012, when it went bust.
The CMA is asking the Supreme Court to rule that the acquisition by Eurotunnel should be treated as a merger.
The authority said it is seeking permission to appeal against the decision announced by the Court of Appeal on Friday.
The CMA says Eurotunnel has more than half the market share of Channel crossings with its rail services and MyFerryLink service between Dover and Calais.
MyFerryLink has been running up to 24 daily crossings using the three former SeaFrance ships.
In January, Eurotunnel was told it must cease its MyFerryLink cross Channel service following a ruling by the Competition Appeal Tribunal.
Court of Appeal judges overturned the decision on Friday with a two-to-one majority verdict.