Emails written by a British Army major serving in Afghanistan condemn the RAF as "utterly, utterly useless", it was revealed today.
They also indicate that more helicopters and manpower are "desperately" needed for the operation to be successful.
The three emails, obtained by Sky News, were penned by an unnamed officer based with 3 Para in the troubled southern province of Helmand.
The major refers to the death of his colleague Corporal Bryan Budd in the Sangin area last month, and describes the soldiers' efforts to save him during an intense fire-fight.
They also outline concerns for two junior colleagues who "look very frightened and slow to react".
"There is a fine line between giving them time to accept what has happened and adjust, and gripping them hard and forcing them to focus," the officer adds.
A spokesman for the Ministry of Defence did not question the authenticity of the emails, saying they were a "moving and at times humbling account of fighting" in Helmand.
"It reflects both how intense the fighting can occasionally be, and the enormous courage, dedication and skill of the British troops operating there."
Defence Secretary Des Browne had already pointed out that British soldiers in the province were sometimes "working to the limits of endurance", the spokesman added.
"The comments this Major makes about the RAF are, however, unfortunate.
"They do not reflect the view of the vast majority of soldiers about the Harrier Force in Afghanistan, which has consistently performed brilliantly in defending coalition forces, so much so that it is in regular demand not just from British commanders on the ground, but from our allies too.
"It must be remembered that this is the opinion of only one man. The general view is very different."
Captain Matt Taylor, 3 Para Operations Officer in Afghanistan, insisted in a statement released by the MoD that the RAF had "played a critical part in ensuring the security of the lads on the ground".
"They couldnt have asked for better support during some very difficult times," he added.
Last night it was reported that another army major, Jon Swift, had claimed that British casualty figures in Afghanistan were being underestimated in official figures.
Major Swift - whose 2 Platoons and Fire Support Group have been supporting 3 Para in the Helmand outpost of Naw Zad - was also said to have criticised the operation as "politically" driven in an interview for the Royal Fusiliers newsletter.
The comments were put up on an MoD-hosted website yesterday, but removed shortly afterwards and the department was unable to confirm their content or authenticity.
The MoD released a text of the newsletter article today in a bid to demonstrate that Major Swift's views had been taken out of context.
Sources at the department said any suggestion of an MoD conspiracy was "absurd and untrue".
The newsletter apparently did not quote Maj Swift verbatim, but stated: "He questioned whether the scale of casualties was being reported in the media as the overall numbers were very significant and showing no sign of reducing.
"He appreciated that the current strategy was following political rather than military imperatives and anticipated that, unless it changed, his Company would likely move and be redeployed in a couple of weeks, although nothing was certain."
Liberal Democrat defence spokesman Nick Harvey said: "The Government must provide an urgent statement in response to these disturbing comments.
"These emails demonstrate the need for a reassessment of the full range of capabilities required to accomplish the Nato mission.
"As our troops face increasing violence, we need to see a clear and achievable strategy and an honest assessment of the challenges ahead."
The unnamed major gives an example of failure of air support in one of the emails.
"From my point of view, controlling and directing air, arty and mors (artillery and mortars) is the best way to influence the battle," he wrote. "The RAF have been utterly utterly useless.
"Twice I have had Harriers in support when c/s on the ground have been in heavy contact, on one occasion trying to break clean.
"A female harrier pilot 'couldn't identify the target', fired 2 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."
In "contrast" to the RAF, the US air force had been "fantastic", according to the major. "I would take an A-10 over Eurofighter any day," he adds.
The battle group are said to have fired more than 300,000 rounds of light ammunition.
This month 19 UK military personnel have been killed in Afghanistan, and ministers have admitted resistance from the Taliban is proving far tougher and more persistent than expected.
Currently Britain has nearly 5,000 troops in the country - including 3,600 in Helmand, with 900 more on the way. The total Nato force is around 20,000. The RAF has seven Harrier fighter jets based there.