An Iraqi police chief cannot trust one third of his officers because they are loyal to illegal militias, he has told the BBC.
General Abdul Hussein Al Saffe, head of policing in Dhi Qhar province, told the BBC's Paul Wood he could not sack them as they had political protection.
British commander Maj Gen Jonathan Shaw said Iraqi ministers knew the police were "not perfect".
But the Iraqis were making a judgement for "self-reliance", he said.
"There's always a balance when you have a newly created police force and army," he said.
"It's a question of balancing Iraqi enthusiasm for self-reliance with the risk of when the are capable of taking that responsibility, and that judgement really has to be made by Iraqis, which they are doing."
Another senior Iraqi officer, Brigadier General Ghalib al Jaza'aere, said he had been forced to hire 300-400 officers who were completely illiterate.
And he said one policeman had been sacked after he was caught smuggling weapons to be used against British troops, only to be later re-instated and promoted by officials in Baghdad.
He even said he feared some members of the police were using torture as they had done under Saddam Hussein.
The officers' comments came as the British handed over their base in central Basra to the Iraqi authorities.
The Iraqi flag was raised over the Old State building, described as one of the most frequently attacked sites in the country.
Platoon Commander Lieutenant Bradley Pino said soldiers there were shot at with guns, rocket-propelled grenades and mortars every night.
Maj Gen Shaw said Tuesday's pullout from the base reflected a real sense of progress felt by British troops.
They were, he told the BBC's Huw Edwards, involved in reconstruction, removing corrupt elements and training Iraqi forces.
"They can actually see what we're achieving on a daily basis," he added.
The British army say Dhi Qhar province is a success story and point out that it is home to the biggest single development project in Iraq, a new gas pumping station costing £10 million.
Colonel Ed Brown, from the Rifles Regiment, is charged with "strategic oversight" of the now fully independent Iraqi forces in Dhi Qhar and neighbouring Muthana province.
He said he had been asked by the Iraqi police for help in dealing with the militia, but had refused.
Col Brown told the BBC: "What we must do as coalition forces is to give as much support as we can without actually taking back the responsibility for security because it is very clearly theirs.
"Things are imperfect, but we make a huge mistake, and we will move down a road that will end in real failure, if we try and turn this into Surrey. It isn't.
"There is a level of violence here, but that is life in Iraq. It's been like this for thousands of years. It's not going to change."