The last chance to save one of the most majestic fish in the sea is on the verge of collapse because of political jockeying in Europe.

A proposal to ban the sale of bluefin tuna is being fiercely opposed by Malta, the capital of the lucrative global business, and by its representative in Brussels, the fisheries commissioner, Joe Borg.

Spain and Italy are also believed to be resisting an application to bar trade in bluefin under the Convention on the International Trade in Endangered Species (Cites), which would cut off exports to the main market, Japan.

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The European Commission will decide next week whether the EU will submit the application to a Cites committee meeting in March.

Conservationists fear that support from Britain, France and other northerly European nations for decisive action is wavering amid the objections.

The Commission is divided, with Brussels sources saying Mr Borg is fighting his environment counterpart, Stavros Dimas, who supports a ban.

Japan has also been lobbying all EU states, telling them that the management of the stock is improving.

Britain describes Japan's approach as "not unexpected", though conservationists accuse Japan of interfering in the EU's internal decision-making. Such has been the controversy that the European Commission President, José Manuel Barroso, is set to take charge of the issue at his cabinet meeting on Thursday.

Groups such as WWF and Greenpeace fear that negotiations to break the deadlock may result in a compromise of the Cites Appendix II listing, which would allow a limited trade that would be used to launder vast quantities of illegally-caught fish. A single bluefin tuna can fetch tens of thousands of pounds on Tokyo's fish markets, making the trade highly valuable for trawlers and ranches that fatten young specimens.

Spotter planes are illegally used to find the creatures in the sea and organised crime in Italy is believed to play a role in illegal "pirate" fishing. The WWF says that breeding stocks of bluefin tuna will disappear within two years at current rates of fishing, although some fear that given the small size of bluefins on the Tokyo fish markets, it may have already collapsed.

In a last-ditch rescue mission this summer, the Mediterranean principality of Monaco suggested bypassing the discredited fisheries body in charge of bluefin, the International Council for the Conservation of Atlantic Tuna (Iccat), by appealing to Cites for an outright ban.

Despite owning a significant bluefin fleet, France threw its weight behind the plan, to the surprise of conservationists. President Nicolas Sarkozy said that decades of over-fishing would have to end. Britain, Germany and other mostly northerly European states with direct financial interest in the fish also expressed support for a ban.

On reaching a final position, the EU's 27 member states will vote as a bloc among the 175-nation meeting of Cites in Doha, Qatar, in March. Other countries are likely to heed Europe's views, given the bluefin is fished in its waters. Such high stakes have led to tense wrangles in Brussels, with commissioners Dimas and Borg again failing to reach agreement in a face-to-face meeting yesterday.

Some conservationists wonder whether Mr Borg may have been influenced by the bluefin tuna industry in Malta, which employs 1,000 of the country's 400,000 citizens and is worth €100m (£87m) a year.

Mr Borg, who will seek Malta's re-appointment to his Commission post in the next month, indicated that he preferred waiting for an update on a rescue plan from Iccat after its next meeting, which would be after the Cites deadline for applications for a ban.

Aaron McLoughlin, the WWF fisheries representative in Brussels, said: "As ever with commissioners, whatever happens at home always grabs special attention. It's a real issue for him, just like the German commissioner will have an interest in all car matters."

Mr Borg's spokeswoman, Nathalie Charbonneau, said any suggestion that he had been influenced by the Maltese government was "false and wrong".

The actors Stephen Fry, Colin Firth and Emilia Fox have written to Mr Barroso, urging him to resist a compromise. Attention on overfishing has intensified since the release this year of the film The End of the Line.

Greenpeace's fish campaigner, Willie Mackenzie, said: "There's incontrovertible scientific proof that the stocks are collapsing. We understand the vast majority of the Commission thinks a ban is the right way to go – scientifically it's the only way to go but politically there's a hurdle to get over."