Mr Clegg has become the most senior politician to question whether the government has the political will to see through its military campaign in Afghanistan.
Amid growing questions over UK strategy, Mr Clegg said casualties were a inevitable fact of war but the government had to show the sacrifices of troops "have not been in vain".
He told the BBC that, "by all accounts", Gordon Brown made a "deliberate decision" not to send more troops because he was "worried by the domestic political reaction".
The failure to provide the necessary resources, in terms of troops numbers and equipment, was a "betrayal" of the "courage and dedication" of troops risking their lives.
"I think we are putting the troops in the worst of all worlds, putting them in harm's way - willing the ends, if you like, but not the means."
He said there was "no evidence" of an overarching strategy linking military progress to reconstruction and aid efforts and this was undermining the fight against the Taliban.
"You cannot fight a war by muddle. You have got to do it properly or not do it at all."
Britain had been "bailed out" by the US, which had sent its own forces into Helmand Province, where the UK and US are conducting a major offensive against the Taliban.
"Gordon Brown has got to stop pretending this is somebody's else conflict."
Mr Clegg emphasised that he had been keen to maintain the cross-party consensus on Afghanistan, formed after the 11 September attacks.
But he said he was concerned by growing casualty numbers and whether recent deaths could have been prevented.
General Sir Richard Dannatt, the head of the British Army, said last month that "more boots" were needed on the ground in Helmand but he did not mind whether reinforcements were British, American or Afghan.
'Hard and dangerous'
Asked if he had been over-ruled over the issue of sending more British troops, he told the BBC.
"The government takes its military advice and it weighs it and it makes its decisions," he said.
"And we have got the troop levels we have."
The latest death on Tuesday took the number of soldiers to die in Afghanistan since the 2001 invasion to 176.
On Wednesday, Defence Secretary Bob Ainsworth defended the government's strategy in the country and warned more lives would be lost.
He said the way ahead in Afghanistan would be "hard and dangerous" but the Helmand offensive was gaining momentum.
The reasons for the UK's continued commitment were "compelling", he said, as isolating the Taliban would make Afghanistan and the whole world more secure.
The Conservatives have said they back the mission's aims but insist the strategy must be clarified.
The SNP have called for a vigorous public debate on the UK's role in Afghanistan including a discussion of a future exit strategy.
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