The Government as a whole gave the public “false and inflated expectations” of what could be achieved by British troops in Iraq, its top military adviser has admitted to The Times.

Air Chief Marshal Sir Jock Stirrup, the Chief of Defence Staff, said that it would take “many years” for conditions to improve substantially in Basra. He also revealed that there were no plans to establish a “permanent British base” in Iraq.

In a wideranging interview, Sir Jock was also sceptical of the call by General Sir Richard Dannatt, the head of the Army, for homecoming parades for troops returning from Iraq and Afghanistan. “I think a lot of units wouldn’t want parades,” he said.

Sir Jock decided to speak out because of his growing concern that the public are failing to appreciate what the British troops have been doing in southern Iraq.

“All they get are snapshots, which are sometimes really good and sometimes really bad,” he said. “In my view, and contrary to what many people may think, the British military in the south of Iraq, against some quite daunting odds, has been successful, and the nonsense about the British having failed in Basra is completely misjudged.”

However, he added: “Of course, it does depend upon recognising what the mission was in the first place, and I’m afraid we did allow some false and inflated expectations to arise. But the mission for the military was to get the place and the people to the state where the Iraqis could run that bit of their country if they chose to.”

He added: “I think we didn’t do a good job, frankly, of setting out the strategic prospect . . . and we have not done as well as we should have done at thinking strategically. I’m talking here not just about the military.”

Privately, Sir Jock believes that all areas of the Government, including the Ministry of Defence and the Foreign and Commonwealth Office, were responsible for heightening expectations of what could be achieved in the country after the invasion.

“I think some people expected that, with the British presence on the ground, we could put Basra society, Basra infrastructure, Basra politics and Basra life back on its feet and make it look like some sort of stable, secure, prosperous urban centre. That is the right aspiration to have, but we could never do that, only the Iraqis could do it,” he said.

Sir Jock’s comments are potentially embarrassing as he is the most senior serving military officer to express such deep concerns over the way the Iraq campaign has been explained to the public. Sir Jock said that there remained huge challenges, which the Iraqis would have to deal with. “I don’t for a moment pretend that there will be a smooth, uninterrupted progress towards some sort of urban idyll in Basra,” he said.

Sir Jock accompanied Gordon Brown on his controversial visit to Iraq on Tuesday when the Conservative Party conference was under way.

Defence sources indicated that Mr Brown had been due to go to Iraq on Thursday or Friday, but that the visit was brought forward by two days. “But that sort of thing often happens when plans are made to fly to Iraq, whoever it is,” one source said.

“The visit to Iraq is something that we had wanted the Prime Minister to undertake. He needed to talk to the key members of the Iraqi Government and form his own assessment before he made his statement to Parliament,” Sir Jock said.

Sir Jock insisted that Mr Brown’s announcement in Baghdad of troop withdrawal was part of long-term strategic thinking. But he was careful to make clear that the decision to announce the withdrawal of 1,000 troops was a matter for the Prime Minister. “You will have to speak to the Prime Minister about the announcements that he makes,” he said.

However, he added: “This is part of a continuing process that has now been running for a year and a half [troop levels reducing from 7,200 in May 2006 to 4,500 by December this year]. It’s a mistake to look at this [the 1,000-man reduction] in isolation.”

Sir Jock, who has remained largely in the background since taking over as Chief of Defence Staff in April 2006, and who has given few interviews, appears to have decided that it was time to make his views clear, particularly after the outspoken public comments about the Armed Forces expressed by General Dannatt, who called last year for British troops to be withdrawn from Iraq “some time soon”.

Sir Jock emphasised the importance of looking after Service personnel who might be suffering from trauma. “My father was in the SAS in the Second World War and he never spoke about it. But when he went to reunions, then he could talk to his old colleagues because they had been through the same experiences,” he said.

The worst aspect of being Chief of Defence Staff had been the toll of casualties in the two military campaigns. “Enjoying [my job] is a difficult word to use when so many people are dying or being injured.

“The key question is, are we gaining strategic advantage in return for the price they are paying? The answer is yes, and if I thought we weren’t, my recommendation would be to end it,” he said. “But it’s a difficult message to get across to the public, and I don’t think we have communicated it very well.”

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