A PR stunt in which Vladimir Putin was presented with water from Lake Vostok, a huge body of water deep under the Antarctic ice, has come unstuck after an official admitted the water did not actually come from the lake.

The Russian prime minister was given the water in a special metal and glass case by Yuri Trutnev, the minister for natural resources, just a few days after scientists had drilled almost 4,000 metres down through the ice to the sub-glacial lake, an event hailed in Russia as a great scientific breakthrough.

An unusually jovial Putin asked the minister during the presentation on Friday how long the water had remained untouched by human hands. On hearing the figure of a million years, he asked him if he had drunk the water and when the minister said no, joked: "That would have been interesting, dinosaurs and Trutnev drinking it."

However, the head of the Russian Antarctic expedition, Valery Lukin, has admitted the water didn't actually come from the lake but from a point before the scientists broke through. There won't be any water taken up from the lake until December this year, he said.

Putin is known for burnishing his image with macho stunts and this is not the first time the truth has proved less than heroic. Last year, Putin's press secretary, Dmitry Peskov, admitted that the prime minister did not really discover two Greek urns on the floor of the Black Sea on a diving trip with archaeologists and that it was, in fact, a setup.