Foreign Secretary William Hague was taken by surprise as Argentina's ambassador urged him at a public meeting to "give peace a chance" by opening talks on the Falkland islands.
Alicia Castro, Argentina's new ambassador to the U.K, ambushed Hague on the subject as he launched Britain's annual review of human rights at an event attended by diplomats, journalists and human rights activists in London.
"Seeing that the United Nations and the international community and a large group of Nobel prize winners urge both countries to (start) negotiations in order to find a pacific and permanent resolution, my question is: Are you ready for dialogue? Are we going to give peace a chance?" she asked as Hague took questions from the audience.
A flustered Hague attempted to interrupt her several times, before cutting her off with "Thank you. That's enough. Stop."
Answering Castro, Hague said: "Self-determination is a basic political right of the people of the Falkland Islands ... You can count on us always, permanently, to stand by that right."
Castro told reporters later that Hague had not answered her question. "You cannot say that you are so good at human rights and democracy if you are not open for dialogue," she said.
Self-determination did not apply to the Falkland islanders, she said.
"Self-determination is not a right that every country has or every population has. A province in my country cannot decide if they want to belong to China."
Asked if she intended to make a habit of appearing at Hague's public events to ask him about the Falklands, Castro laughed and said: "You wait and see".
Castro met foreign minister Jeremy Browne last week and handed over notes requesting talks with Britain on air links with the Falklands and South Atlantic fisheries.
Britain maintains that the Falklands are self-governing and that Argentina must talk to the islanders about such matters.