The RAF are "utterly, utterly useless" in protecting troops on the ground in Afghanistan, a major with the main UK battle group says in a leaked e-mail.
UK troops in Afghanistan are coming under sustained attack
Major James Loden of 3 Para, based in the north of the southern province of Helmand, said more troops and helicopters were desperately needed.
He said "plenty of tears" had followed casualties lost fighting the Taleban.
The head of the British Army, General Sir Richard Dannatt, hit back, saying the RAF had performed "exceptionally".
"Irresponsible comments, based on a snapshot, are regrettable," he added in a statement.
The Ministry of Defence had earlier confirmed the e-mail was genuine.
The "tears" Maj Loden refers to were "not tears of exhaustion or frustration", a spokesman said.
"This is a reflection of the fact these men are under daily attack and sadly there are often daily casualties."
Describing Maj Loden's e-mail as "moving" and "humbling", the spokesman said it "reflects both how intense the fighting can occasionally be, and the enormous courage, dedication and skill of the British troops" in Helmand.
Some were "working to the limits of endurance, but their morale is high and they are winning the fight", he added.
Maj Loden's comments about the RAF "do not reflect the view of the vast majority of soldiers", the spokesman said.
It had "performed brilliantly in defending coalition forces", he added.
But Maj Loden's e-mail gives an example of the RAF's failure to provide air support.
"... Harrier pilot 'couldn't identify the target', fired two phosphorous rockets that just missed our own compound so that we thought they were incoming RPGs [rocket-propelled grenades], and then strafed our perimeter, missing the enemy by 200 metres," it says.
BBC defence correspondent Paul Wood said Maj Loden's comments reflected what officers were saying privately, but their tone and emphasis were at odds with the MoD's official statements.
Other Parachute Regiment officers had told him they prefer to call in American A-10 Tankbusters for air support when under fire because of what they see as the RAF's ineffectiveness, he added.
However, in a statement released by the MoD, 3 Para operations officer in Afghanistan Capt Matt Taylor said the RAF had "played a critical part in ensuring the security of the lads on the ground".
"They could not have asked for better support during some very difficult times," he added.
UK INJURED: AFGHANISTAN
Wounded in action: 37
Non-battle injuries: 40
Very seriously ill: 4
Seriously ill: 5
Medical evacuations: 125
1 January - 31 July 2006
Gen Dannatt said he had visited Afghanistan since the incident described in the e-mail and said: "The men of the Battlegroup left me in no doubt as to the RAF's support of their operations."
British spokesman in Southern Afghanistan Lt Col Dave Reynolds added the RAF was an "enormously effective", "invaluable" and "absolutely essential part of the operations in Afghanistan".
Liberal Democrat defence spokesman Nick Harvey called on the government to "provide an urgent statement" in response to Maj Loden's "disturbing comments".
His e-mail showed "the need for a reassessment of the full range of capabilities required to accomplish the Nato mission" in Afghanistan, Mr Harvey added.
"As our troops face increasing violence, we need to see a clear and achievable strategy and an honest assessment of the challenges ahead."