LONDON (Reuters) - Britain was not given prior notice of the Algerian government operation to release hostages at the remote gas plant where they are being held and would have preferred to have been informed, Prime Minister David Cameron's spokesman said on Thursday.

Cameron had called his Algerian counterpart Abdelmalek Sellal at around 1130 GMT on Thursday.

"The Algerian Prime Minister explained that the situation was very fast-moving and that in the government's judgment they needed to act immediately," the spokesman said.

"The Algerians are aware that we would have preferred to have been consulted in advance," he added.

Cameron told Sellal after the operation started that he was extremely concerned about the "very grave and serious" situation, the spokesman added.

(Reporting by Mohammed Abbas; Editing by Stephen Addison)