Iraq's interim president says the United States and Britain made a huge mistake by dismantling the Iraqi army after toppling Saddam Hussein.
The president said coalition actions had created a vacuum
Ghazi Yawer told the BBC this had created a security vacuum that was partly to blame for the violence.
"We could have screened people out instead of screening them in, and this could have saved us a lot of hassle and problems," he said.
The UK's Iraq envoy said the problems had only become clear with hindsight.
Mr Yawer told BBC Radio 4's Today programme the main task facing the interim government was to ensure Iraqis could vote safely in the 30 January election.
He blamed some of the present difficulties on the US decision to break up Saddam Hussein's entire security apparatus as soon as American-led forces had toppled the dictator last year.
By a scratch of the pen, he said, many men with a clean record were forced out of the security forces along with "the villains".
"We have to reinstate some of the clean-record army officers and police officers," he said.
But the president said Iraqis on their own could never have toppled Saddam Hussein.
"Toppling Saddam's regime is the biggest plus that we will never regret happening. He left no choice for Iraqis because he established a dynasty of villains," he said.
Later, the UK's ambassador to Iraq, Edward Chaplin, told the BBC's Newsnight programme: "Everyone realises with hindsight that perhaps things could have been done differently.
"But the first thing to remember is that the army wasn't so much disbanded as it simply melted away. And there was a lot of very strong feeling at the time that it was quite unthinkable to rehabilitate an instrument of Saddam Hussein's regime," he said.
He said a strong leadership for the security forces now had to be created - and that might entail bringing back some people, "with proper vetting".