Lt Col Thorneloe died in an explosion near Lashkar Gah in July
The most senior British officer to be killed in the Afghan campaign had warned about the risks posed to troops by a shortage of helicopters.
Lt Col Rupert Thorneloe, 39, commanding officer of the 1st Battalion, Welsh Guards, died in a roadside bombing.
In memos leaked by an official to Tory MP Adam Holloway, a former officer, Col Thorneloe said too many trips were by road, leaving forces vulnerable.
The government had denied an absence of helicopters led to deaths.
Col Thorneloe was killed on 1 July along with Trooper Joshua Hammond, during Operation Panther's Claw, the offensive against insurgent strongholds in Helmand.
Their convoy was hit by an improvised explosive device (IED) near Lashkar Gah.
Adam Holloway: "There are not enough helicopters, and there never have been"
In memos sent three weeks earlier and published in the Daily Mail, he warned his brigade commanders in the UK about a shortage of helicopters in Helmand, and the increased risks posed to British troops.
"I have tried to avoid griping about helicopters - we all know we don't have enough," he wrote.
"We cannot not move people, so this month we have conducted a great deal of administrative movement by road.
"This increases the IED threat and our exposure to it."
Col Thorneloe, from Kirtlington, near Oxford, said he had "virtually no" helicopters of the type which would allow him to move troops by air rather than road.
He also termed the system used to manage helicopter movements in Afghanistan as "very clearly not fit for purpose".
Responding to the disclosure of Col Thorneloe's memos, Defence Secretary Bob Ainsworth said the use of helicopters had increased.
We know the value of helicopters on operations and that is why we have increased the numbers
"We know the value of helicopters on operations and that is why we have increased the numbers and types, improved engines and almost doubled flying hours."
He said additional Merlins were being deployed and more Chinooks would be sent during the coming year.
He added: "To counter the roadside bomb threat we have also been improving unmanned air surveillance and provided more and better protected vehicles."
However, Mr Holloway said the memo was "devastating" for the government.
"It just shows they aren't taking this war seriously," he said.
"For the last three years we've been told constantly by the government that our guys have got enough helicopters to do the job.
"Anybody who's visited Afghanistan and spoken to the soldiers knows there simply aren't enough helicopters and there never have been."
Twenty-two British soldiers died in Helmand in July, the majority of them killed by improvised explosive devices.
The deaths sparked a debate about helicopter shortages in the armed forces, with Chief of the Defence Staff Sir Jock Stirrup suggesting the deployment of more to Afghanistan would save soldiers' lives.
However, Sir Jock told BBC Radio 4's Today programme that while more helicopters would always help operations in Afghanistan, there had been sufficient numbers for this summer's operations.
Chief of the Defence Staff, Sir Jock Stirrup: "Helicopters themselves are not a panacea"
He said Col Thorneloe's comments related to the deployment of craft within Afghanistan.
"The key element of criticism was inflexibility of allocating helicopter assets within theatre, which to Rupert didn't seem to make sense," said Sir Jock.
"He was saying that if we allocated the helicopters in a different way, we would get more available."
The prime minister has told parliament that the armed forces were better equipped than ever and it was wrong to say that deaths had been caused by a shortage of helicopters.
In response to a suggestion that more helicopters would "patently" save troops' lives, Mr Brown said in July: "More helicopters in general, yes. That is why we are putting them, of course, into Afghanistan. More helicopters are being ordered for Afghanistan.
"But in the operations we are having at the moment it is completely wrong to say that the loss of lives has been caused by the absence of helicopters."
He added: "For the operation we are doing at the moment we have the helicopters we need."
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