Argentina has told an international tribunal that Britain’s approval of oil drilling off the Falkland Islands has dramatically deepened a sovereignty dispute that led to war four decades ago.

At the start of an historic legal clash at the Hamburg-based International Tribunal for the Law of the Sea (Itlos), an Argentinian legal team argued that the oil project must be suspended.

Javier Oyarzábal, chief legal adviser to Argentina’s ministry of foreign affairs, said that the 3,400 inhabitants of the Falkland Islands, whose status as a British overseas territory is disputed by Buenos Aires, had no right to the resources around the south Atlantic archipelago.

Oyarzábal said: “[Argentina] respects the interests of the inhabitants of the islands and their way of life as enshrined in the Argentine constitution … What these British citizens do not have is a right to decide to which state the islands belong …

“These resources belong to the Argentine people. Some 46 million of them including the 1,247 inhabitants born on the islands whose interests will be duly taken into account.”

Oyarzábal said Argentina was ready to negotiate “all aspects of the question” of the Falkland Islands, which are known as the Malvinas in Argentina, “including the present aggravation of the dispute caused by the UK”.

He accused the UK of refusing to enter talks over the islands while pushing forward on the exploitation of its natural resources in a way that would entrench the status quo.

Oyarzábal claimed that the oil money from the drilling would “finance the very military base and presence that sustains the UK’s de facto control of the territory”.

Addressing the panel’s chair, Judge Maurice Kamga, from Cameroon, he added: “Mr President, the UK cannot have it both ways. It cannot invoke the sovereignty dispute to escape jurisdiction [of Itlos] while exploiting the natural resources of the disputed area as if a dispute had already been resolved in its favour.”

The Sea Lion project in the North Falkland basin, led by the Israeli-firm Navitas and its British partner, Rockhopper, has the potential to triple the islands’ GDP per capita.

It has been condemned as unlawful by Argentina’s president, Javier Milei, and his government has applied for arbitration by Itlos over the future of the project, claiming Britain’s approval of is in breach of a 1976 UN resolution calling on both parties to desist from unilateral action on the islands until the sovereignty dispute is settled.

Argentina is requesting urgent provisional measures, including a commitment from the UK to “stop the drilling” which, Oyarzábal said would do no more than “preserve the present situation” and allow for constructive talks over sovereignty to begin.

At the start of the two-day hearing, the tribunal’s panel was told that a decision by the UK government to allow drilling to start in March next year was the “unilateral conduct” of a “colonial power”.

It was further claimed by Argentina that the Sea Lion oil project risked an environmental disaster on Argentina’s doorstep and that it would make the sovereignty dispute over the islands “more difficult or impossible” to resolve peacefully.

He added: “In the event of a blowout or spill, it is Argentina that would bear its consequences and be called upon to respond, not a state that is 12,700km away. More over the project lies within the search and rescue region for which Argentina is responsible”.

The long-standing dispute between Argentina and the UK over the sovereignty of the Falklands led to war in 1982 at the cost of the lives of 649 Argentine military personnel, 255 British military personnel and three Falkland Islanders.

The hearing is the first time that substantive matters relating to the Falklands have been litigated at an international tribunal.

The oil project is seen on the islands as offering the opportunity to secure their economic future, and build a sovereign wealth fund, at a time when fisheries catches on which they depend are declining.

In a show of solidarity, Princess Anne arrived in Port Stanley on Monday. Ellie Reeves, the UK’s attorney general, attended the Itlos hearing on Tuesday.

She claimed that Argentina was seeking to litigate the issue of sovereignty through Itlos, an independent judicial body established by the 1982 United Nations convention on the law of the sea to oversee maritime disputes.

She said: “We don’t think this is the forum to effectively determine sovereignty issues.”

Asked whether the UK would abide by any ruling, Reeves said: “We don’t know what’s going to happen in terms of the outcome but we don’t consider they have jurisdiction on sovereignty issues. We respect the court and the institutions … but I don’t want to get ahead of what the tribunal may or may not say.” The hearing continues.