Peter Galbraith, who left his post as deputy head of the UN mission in Afghanistan amid disagreements over the presidential elections, has been speaking about the killing of five UK soldiers at the hands of a rogue officer.
He blamed the "rushed" bid to train extra Afghan officers for the poll.
"It is a terrible tragedy but it is, I won't quite say inevitable, but it is not surprising," he told the BBC Radio 4 Today programme.
"The process of police training and recruiting has been very rushed. Normally the police get an eight-week training course. That is actually very short and there isn't a lot of vetting of police before they are hired.
"And actually, in recent months, they shortened the training programme from eight weeks to five weeks because they wanted to get more police boots on the ground in advance of the elections. So there was a real rush to recruit an additional 10,000, particularly in the south, particularly in Kandahar and Helmand provinces.
"So it is not totally surprising that people were recruited who may have had Taliban sympathies or were infiltrated into the police by the Taliban although I don't know yet whether in this particular episode that is exactly what happened."
The undermining of the legitimacy of the Afghan government because of the "chaos" surrounding the election had also "created opportunities for the Taliban," he said, sending his condolences to the families of those killed in the incident.Reuse content