West Australian moderate Mal Washer believes Australia is only involved in the conflict "to appease the Americans".
"Andrew says we might have blood on our hands," Dr Washer told ABC Radio on Saturday.
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"Certainly, I feel like that it's on my hands and that's why I speak out against this. This is utter stupidity."
Dr Washer's comments come just days after five Australian soldiers were killed in Afghanistan in a 24-hour period.
A rogue Afghan soldier shot dead three diggers and wounded two others on Wednesday night.
Two special forces soldiers died in a separate incident on Thursday morning when a US Blackhawk helicopter crashed.
Mr Wilkie said on Friday the five soldiers "died unnecessarily" and Prime Minister Julia Gillard and her predecessors Kevin Rudd and John Howard "all have blood on their hands".
"Being in Afghanistan now is not in Australia's national interest," the former soldier said.
Ms Gillard brushed off those comments, saying she wouldn't get sidetracked by domestic debate "even if some ugly language has been used".
Dr Washer on Saturday said Afghanistan was hardly a threat to Australia's security.
After 10 years it was evident the task of training the Afghan army had failed, he said.
"We haven't been too successful when they start shooting us."
But senior Liberal Christopher Pyne was quick to dismiss Dr Washer's remarks.
He said Canberra had had the same "national policy" on Afghanistan since the September 11 terrorist attacks in 2001.
"We don't want to send a message to our opponents, the Taliban, or anyone who promotes terror around the world, that if they kill our Australian soldiers we'll lose heart and leave," Mr Pyne told Sky News.
The opposition frontbencher said Mr Wilkie went "far too far" in his comments which were "completely inappropriate". But he was less critical of his own colleague.
Dr Washer was entitled to his opinion even though it wasn't the official view of the Liberal Party, Mr Pyne said.
"I have a great deal of respect for Mal Washer. He's a good friend of mine, but on this occasion I'm afraid I have a much more hawkish view about what needs to be done in the war on terror."
Also on Saturday, US Secretary of State Hillary Clinton telephoned Ms Gillard to offer her condolences.
"Secretary Clinton called to offer her personal condolences for Australia's terrible losses in Afghanistan," Ms Gillard's spokeswoman said in a statement.
"The prime minister and the secretary agreed on the vital importance of ISAF (international forces) and the Afghan government taking the strongest possible measures to reduce the risk of insider attacks on coalition forces."
Seven Australians have now died in so-called "green on blue" attacks by allied Afghan national army soldiers.
The latest perpetrator, Hek Matullah, has been pursued since Wednesday, when he scaled a fence and ran for his life after he opened fire on the diggers with an automatic weapon.
The names of the three soldiers shot at close range remain undisclosed.
The two soldiers killed in the helicopter crash were Lance Corporal Mervyn McDonald, 30, of Carnarvon, Western Australia, and Private Nathanael Galagher, 23, of Wee Waa, NSW.
