David Cameron has called Vladimir Putin and urged for "prompt, fair and proportionate action" from Russia over the case of the detained Greenpeace activists.
A Number 10 spokesman confirmed a phone call took place yesterday and said: "President Putin was understanding of the Prime Minister's concerns. They agreed to stay in touch on the issue."
Greenpeace has made a film to mark the first 50 days since 30 people on board its ship, the Arctic Sunrise, were detained by the Russian authorities.
They were initially charged with piracy, although it was later changed to hooliganism, which carries a lesser sentence.