Survivors and relatives of Britain's worst maritime disaster are considering legal action to have the site designated a maritime war grave.
The Lancastria sank of the French coast in 1940.
The Clyde-built Lancastria was carrying about 9,000 troops when it was sunk by German bombers off the coast of France in 1940 during a mass evacuation.
The Tayside-based Lancastria Association of Scotland's move came after a decision in a similar case.
But the Ministry of Defence said the UK had no legal power over the Lancastria.
About 4,000 people died in the disaster - the single biggest loss of life for British troops in the whole of WWII.
It lies in about five miles from the French coastal town of St Nazaire in about 20m of water.
The French government has already given the wreck special protected status after concerns about divers intruding on the site.
And the MoD said the UK did not have legal powers to designate the Lancastria a maritime war grave because of the location of the wreck, inside French territorial waters.
The move by the Lancastria Association of Scotland came after campaigners won their battle to have a naval wreck off the Sussex coast classed as a war grave.
The Court of Appeal upheld an argument that the SS Storaa, which sank in 1943, had been on military duties.
The association, based in Abernethy, is now considering an application to the High Court in London in a bid to have the Lancastria designated under the Protection of Military Remains Act.
The group's chairwoman Fiona Symon, whose father Andrew Richardson was killed aboard the Lancastria, said: "There is a great deal of disappointment among the relatives of victims and survivors that we are having to consider such a course of action.
"Designation should have been granted automatically for those who were killed in action on these ships and who gave the ultimate sacrifice for their country."
Ms Symon added: "What we are asking the UK Government to do is to afford the victims the same respect and dignity which the French Government have given them and finally designate this British wreck an official maritime war grave."
A petition on the Lancastria campaign is due to be handed into Downing Street in the New Year.