David Cameron took at a swipe at Argentina for undermining attempts to restore global growth through protectionist measures on trade.
Relations between Britain and Argentina are in the deep freeze after Buenos Aires tried to use the 30th anniversary of the Falklands War to revive its claim on the islands it knows as the Malvinas.
Mr Cameron is expected to use an opportunity to speak to Argentine President Cristina Fernandez de Kirchner in the margins of the G20 summit in Mexico on Monday in order to make Britain's position on the disputed islands clear to her face.
The prime minister is expected to restate the UK's insistence that it will not enter into negotiations about the future of the islands against the wishes of the Falklanders, who are expected to say in a referendum next year that they want to remain British subjects.
And Mr Cameron had a tough message for Argentina on trade too, singling them out as offenders over protectionism - which he today identified as one of the five key threats to global recovery.
Speaking to a business audience ahead of the official opening of the Los Cabos summit, Mr Cameron did not mention Argentina by name, but said that there was "one G20 member" which had imposed protectionist measures which threatened to harm the global economy.
There was no doubt that his comments referred to Argentina, which earlier this year sparked fury by nationalising the oil company YPF, largely owned by Spanish firm Repsol.
Buenos Aires has also imposed new requirements on the movement of financial assets designed to shore up its own economy.
Mr Cameron said: "In the last eight months investment... has been subject to restrictive measures.
"We have seen the expropriation of a multinational company, requirements that export revenues in oil, gas and mining sectors be exchanged in local financial institutions, new regulations on foreign exchange assets of residents, insurance companies required to repatriate foreign assets and limits imposed on investment in farm land - and that is just from one G20 member."
Mr Cameron has met Ms Kirchner on the fringes of previous international summits, but has yet to hold a formal bilateral meeting with her. No such meeting is expected in Mexico this week.
Ms Kirchner last week addressed a United Nations Decolonisation Committee and demanded that Britain enter discussions about the future of the Falklands.
But Foreign Office minister Jeremy Browne rejected an invitation to travel to Buenos Aires for talks during his visit to the islands for commemorations to mark the anniversary of the war last week.
Mr Cameron said: "The Falkland Islanders have decided to have a referendum.
"They are going to ask a very simple question of whether they want to continue with the status quo or whether they want to change.
"The message to Argentina is very clear - listen to what the people of the Falkland Islands want.
"We should all believe in this day and age in self-determination, not colonialism."
Asked if he would pass this message directly to Ms Kirchner, Mr Cameron said: "Absolutely."