Lord Guthrie: "There is a clear need for more helicopters"
Three ex-chiefs of the defence staff have launched a scathing attack on Gordon Brown's commitment to the war in Afghanistan and support for UK troops.
Lord Boyce said the government "did not realise we are at war" while Lord Inge said the armed forces never really believed Mr Brown was "on their side".
Lord Guthrie, meanwhile, accused Mr Brown of "dithering" over his pledge to send 500 more troops to Afghanistan.
The government said troop numbers had increased and they had enough kit.
The stinging criticism from three of the UK's most respected military figures came just hours after Mr Brown said the UK would not "walk away" from its Afghan commitments and would "succeed" in its mission.
It also comes ahead of the Remembrance Sunday and Armistice Day commemorations.
I do think that military services, the people in the front line, are questioning whether the government is really, really committed to making progress in Afghanistan
In a speech in London, Mr Brown said it was "simply wrong" to say troops were not getting the support they need, saying Labour had spent £1bn on new armoured vehicles for troops serving there since 2006.
He said he was determined to do everything necessary to protect UK troops, especially from the deadly threat of roadside bombs.
Mr Brown also used the speech to warn Afghan President Hamid Karzai he will not put UK troops "in harm's way for a government that does not stand up against corruption".
The disagreement with the ex-generals underlines Downing Street's increasingly uncomfortable relationship with retired generals in recent months, as public criticism of troop numbers and resources in Afghanistan has intensified.
So far, 93 UK service personnel have been killed in 2009 - the highest toll in a single year since the Falklands campaign 27 years ago.
Speaking in a debate on the armed forces in the House of Lords, Lord Boyce, Chief of the Defence Staff between 2001 and 2003, said the UK was in the middle of a "defence train crash".
Field Marshall Peter Inge served as chief of the defence staff between 1994 and 1997, entering the House of Lords in 1997
General Charles Guthrie served in the army for more than 40 years, latterly as chief of the defence staff between 1997 and 2001
Admiral Michael Boyce was First Sea Lord before serving as chief of the defence staff between 2001 and 2003
"It is too much to hope that the present government will provide the necessary cash to allow its aspirations to be realised properly or honourably," he said.
"Government does not realise we are at war."
He said defence spending was falling as a share of national income and frequent changes at the top of the Ministry of Defence - where there have been four secretaries of state since 2006 - had been destabilising.
Lord Guthrie, who preceded Lord Boyce as head of the UK's armed forces, said that if more helicopters had been available to UK forces over the past year then lives would have been saved.
"I do think that military services, the people in the front line, are questioning whether the government is really, really committed to making progress in Afghanistan," he said.
The peer, who was chief of the defence staff between 1997 and 2001, criticised No 10's decision to make the mobilisation of a further 500 troops conditional on Nato allies boosting their own numbers, and the Afghan government being prepared to train more of its own soldiers.
If commanders on the ground had requested the troops, he said they should be sent regardless of political concerns.
And speaking about the extra troops, he told peers: "(They) are available, they are waiting and because of what appears to be dithering in London, are becoming unsettled."
Separately, Lord Inge claimed that the prime minister had "some baggage" as far as support for the armed forces was concerned.
"They have felt he has never really been on their side and they have not had his support," he said.
Defence Secretary Bob Ainsworth told BBC Radio 4's World at One: "Lord Guthrie has been making this same speech sadly for some time now.
Caroline Wyatt, BBC defence correspondent
In a phrase that may dismay military commanders, the Prime Minister said of the international coalition that "in the end we will succeed or fail together". Talk of failure is not something commanders or troops on the ground want to hear.
"We have been been very clear. Our troop numbers have gone up and have gone up quite considerably. There were 8,100 at the start of the year, there are 9,000 on an enduring basis now. We have said we will put another 500 in if certain conditions are met."
The defence secretary also indicated he would welcome a swift announcement from US President Barack Obama on whether he is going ahead with the 40,000-strong troop surge recommended by the head of the ISAF international force in Afghanistan, General Stanley McChrystal.
"I would like to see President Obama respond to Gen McChrystal's plan as soon as he is able to, but I do not blame him for wanting to look at this in some detail," said Mr Ainsworth.
"We have already seen a huge uplift in American troops in Afghanistan. Gen McChrystal is asking for more and President Obama knows that the overwhelming majority of those will have to be American in the first instance."
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