An ex-chief of the defence staff has said the deployment levels of British soldiers in Afghanistan are "cuckoo".
Lord Guthrie was one of Tony Blair's most trusted commanders
Lord Guthrie told the Observer anyone who thought the mission would be a "picnic" did not know its history.
His words will be seen as an attack on ex-defence secretary John Reid who said when he committed troops he hoped they would return without "firing a shot".
Lord Guthrie also cast doubt on Tony Blair's claim he would give the army the extra resources it needed.
He said the prime minister was "not dishonest" but his good intentions in Afghanistan would be difficult to fulfil.
"There is no way you can magic up trained Royal Air Force crews, or trained soldiers, quickly.
"You can't magic up helicopters, because there aren't any helicopters," said Lord Guthrie who was among Mr Blair's most trusted commanders before he quit in 2001.
John Reid, now the home secretary, launched the mission in Afghanistan in Kabul by saying: "We would be perfectly happy to leave in three years time without firing a shot because our job is to protect the reconstruction."
The ministry of defence has subsequently admitted it has faced tougher resistance from the Taleban than expected.
Lord Guthrie told the Observer: "Anyone who thought this was going to be a picnic in Afghanistan - anyone who had read any history, anyone who knew the Afghans, or had seen the terrain, anyone who had thought about the Taleban resurgence, anyone who understood what was going on across the border in Baluchistan and Waziristan - to launch the British army in with the numbers there are, while we're still going in Iraq, is cuckoo."