Foreign Secretary David Miliband said payments were, "only an encouragement to further hostage-taking". His Saudi counterpart Prince Saud Al-Faisal said owners Vela International are in talks with the pirates.
"We do not like to negotiate with either terrorists or hijackers," but, he added: "The owners of the tanker are the final arbiters of what happens there."
A foreign news agency reported that the pirates have demanded 25 million dollars (£16.6 million) for the hostages' safe release. But Vela would not confirm this figure and maritime security experts said the true ransom is expected to be much higher.
A spokesman for the Foreign Office said British policy was not to negotiate with hijackers but conceded the Sirius Star, "is not a British ship".
"I cannot say if we have been contacted (by the pirates) or not. That is not something we can get into discussing," he said.
The UN approved a British proposal to impose new sanctions against Somalia in a bid to cut off the pirate gangs. It also called on the security council to recommend the freezing of assets of individuals and organisations.
Mr Miliband said he was "extremely concerned" about the situation and called on the international community to "stand firm" against hostage-taking in all its forms.
Author: Jo Amey
