The Algerian government kept David Cameron in the dark about plans to launch a military rescue mission for the hostages held captive by militants, it has emerged.
Downing Street confirmed on Thursday afternoon that the prime minister had asked his Algerian counterpart to consult Britain before any military moves were made, given the presence of "several" British hostages.
However despite the request to be kept informed, Cameron was only formally told of the military action after it had begun on Thursday morning.
The PM called Abdelmalek Sellal, the Algerian prime minister, at 11.30am today to find out the latest development.
During the 10-15 minute conversation Sellal told Cameron it had been his judgment that he had needed to act "immediately".
According to the prime minister’s official spokesperson, Algeria was aware Britain would have “preferred to have been consulted in advance” but chose to ignore that request.
"The prime minister is extremely concerned. It is a very grave and serious situation," the spokesman said.
However the spokesperson refused to be drawn on whether Cameron only became aware of the military action during the phone call, or had learned of it prior to placing the call.
“We are in constant contact with them [Algeria], it’s a fast moving, ongoing situation and we are doing as much as we can to establish what is going on," he said.
The spokesperson would also not be drawn on reports that between six and 35 hostages and between eight and 15 of the rebels had been killed in the fighting.
The British government has offered to provide assistance if asked – but such as request has yet to be made by Algeria.
It is understood that Algeria did not inform other foreign governments about its decision to launch an operation.
Cameron has also had phone conversations with French president Francois Hollande and US president Obama to discuss the situation in Algeria.
The prime minister was due to chair another meeting of the emergency Cobra cabinet committee later on Thursday to assess the situation.
The prime minister has now cancelled his trip to the Netherlands, where he was due to deliver a speech on the European Union, in light of the escalating crisis.