Russian authorities are refusing to grant visas to a group of environmental campaigners facing charges of hooliganism over a protest at an oil platform.
Greenpeace says Russia's powerful Investigative Committee has written to one of the so-called "Arctic 30" protesters indicating she is not free to leave the country.
It means all of the non-Russians members of the group, including Tasmanian Colin Russell, could be forced to stay in St Petersburg for Christmas and "possibly well beyond", the organisation says.
The group of 30 was arrested in September during a protest at a Russia offshore oil drilling platform.
Mr Russell was the last of the group to be granted bail and was eventually released from jail on December 1.
The group is awaiting visas to allow them to leave the country.
Last week lawyers for the Arctic 30 asked the committee to contact the Federal Migration Service (FMS) and request visas for the non-Russians, so they can leave Russia and return if summoned by the authorities.
But in its letter to Danish woman Anne Mie, the committee said it is not willing to ask the FMS to issue the visas, Greenpeace said on Saturday.
The decision goes against a ruling in November by the International Tribunal for the Law of the Sea (ITLOS), which ordered Russia to allow the Arctic 30 to leave the country immediately and to release the Greenpeace ship Arctic Sunrise, as soon as a bond of 3.6m Euros was paid.
"I am ready to go home to my family," captain of the Arctic Sunrise, Peter Willcox, said.
"We were seized in international waters and brought to Russia against our will, then charged with a crime we didn't commit and kept in jail for two months.
"A respected international court says we should be allowed to go home, so do numerous Presidents and Prime Ministers, but we can't get visas to leave the country."
