At en afghansk offiser går løs på britiske medsoldater og dreper tre før han flykter, er med å undergrave tilliten mellom soldatene og britenes tro på krigen.
Det er andre gang på relativt kort tid at en afghansk militær går amok med våpenet og forsøker å drepe så mange briter som mulig.
A British general said the killer, a senior non-commissioned officer holding the rank of sergeant or higher, may have been «turned» by the Taliban.
Last night the Taliban claimed the Afghan soldier had joined its insurgency.
In a message on its website, Qari Yousef Ahmadi, the Afghan Taliban spokesman, said that after opening fire on the sleeping servicemen the rogue soldier fled to a location protected by the Taliban.
The incident has raised fresh concerns about the Western strategy for Afghanistan, which is based on training and enlarging the Afghan National Army until its members can secure the country themselves.
Describing the killings as «appalling», David Cameron insisted that the incident would not alter Britain’s approach or weaken the Government’s resolve.
But one defence expert said that the «betrayal of trust» could undermine British support for the war, which has now lasted nearly nine years and resulted in 317 British deaths.
The incident has also highlighted doubts about the reliability of the Afghan security forces, whose members have carried out at least three attacks on British forces in recent years.
But Prof Michael Clarke, the director of the Royal United Services Institute, warned that the latest killings could undermine British commitment to the Afghan deployment. He said: «The betrayal of trust has a very high symbolic value and the danger is that is corrosive of public opinion and public support for the mission. That genuinely worries senior commanders.
«The fact that he [the killer] was a senior NCO is a worry – he was not a raw recruit just out of basic training, he was a senior man, someone who was trusted and respected.»
One British Army source said: «It massively undermines our exit strategy. Without a functioning Afghan police and army there is no way we can begin reducing our forces.»
Rogue Afghan soldier murdered senior army officer in his sleep
A Senior British Army officer murdered in his sleeping quarters was among the three victims of a rogue Afghan soldier.