The Ministry of Defence has rejected claims by a warlord that Prince Harry "kills innocent Afghans while he is drunk" as "simply absurd".
Gulbuddin Hekmatyar, a former Afghan prime minister who leads the militant group Hizb-i-Islami, also claimed that foreign forces in the country have failed.
He told the Daily Telegraph that Prince Harry, who has been serving in Afghanistan since September as an Apache helicopter co-pilot, was a "jackal" who was drunk on duty.
"The British prince comes to Afghanistan to kill innocent Afghans while he is drunk," said Hekmatyar, who has been in hiding since the mid-1990s.
"He wants to hunt down Mujahideen with his helicopter's rockets, without any shame.
"During the Mujahideen's attack on the American base the prince saw that he was the one about to be hunted and was searching for a hole in which to hide himself."
Hekmatyar is considered a terrorist by the USThe Ministry of Defence said it was "simply absurd" to suggest that the third-in-line to the throne or any other member of the British armed forces was conducting operations under the influence of alcohol.
"The consumption of alcohol by UK military personnel is not permitted under any circumstances while deployed in Afghanistan," a ministry spokesman said.
A military source also dismissed Hekmatyar's comments, saying: "The idea that highly skilled and professional Apache pilots operate drunk is patently ridiculous and completely made up.
"It is nothing more than a see-through attempt to undermine the very real progress being made in Afghanistan by UK troops and their Afghan partners."
Hekmatyar founded Hizb-i-Islami, notorious for its bloody siege of Kabul in the 1990s, and is considered a terrorist by the US.
Prince Harry has been in Afghanistan since SeptemberIn the interview, Hekmatyar also accused Britain of being dragged into the war to please its American allies and said its role in the conflict would have no significance after 2014.
"Britain dragged herself into this unjustified, useless but cruel conflict to please the White House," he said.
"The British did not gain anything, instead they lost blood and treasure. They never had a positive role in Afghan affairs and they will not have any significance after 2014.
"I don't understand how the British public accept their children being sent to certain death in order to please American generals."
The interview comes just weeks after UK Prime Minister David Cameron signalled that British troops could be withdrawn from Afghanistan even faster after better-than-expected progress by the country's own security forces.
But Hekmatyar said: "The fact is that the government has failed. The authorities have lost their credibility completely. They have fallen victims to severe internal disputes and seem hopeless and worried.
"We might have a dreadful situation after 2014 which no one could have anticipated."
The Nato coalition has been fighting the Taliban insurgency for 11 yearsThe MoD spokesman said: "UK troops deployed and remain in Afghanistan to protect our national security by removing what was a safe haven for international terrorism.
"Now, it is Afghan forces that now have lead security responsibility for around 75% of the population in the country and lead up to 80% of conventional partnered operations.
"It is this sort of progress that has allowed almost 60% of UK bases in Helmand to be shut or handed over and will allow us to leave a stronger more secure Afghanistan when combat operations cease by the end of 2014."
Hekmatyar's Hizb-i-Islami, which means Islamic Party, has widespread national support in Afghanistan and shares some of the Afghan Taliban's anti-foreigner, anti-government aims, and wants to oust international forces.
The US State Department has listed Hekmatyar as a "terrorist" since 2003 for supporting Taliban and al Qaeda attacks.
Hekmatyar is a fierce rival of Taliban leader Mullah Omar, and became a hero to many Afghans while leading mujahideen fighters against the Soviet occupation of Afghanistan in the 1980s.