I missed this BBC Radio 4 programme, but the News website has a story on the issue and this appears in a side-bar.

Captain Doug Beattie has completed 3 tours of Afghanistan, most recently with the Territorial Army. He told File on 4 about the tribal allegiances which conflict with the work of many Afghan recruits.

There is a podcast for File on 4, but not yet this programme:http://www.bbc.co.uk/podcasts/series/fileon4

Do not think of the Afghan Police as your local policeman who really looks after criminality. What you're looking at is a man who is normally illiterate, who is heavily armed, but has no concept of the rule of law. This young man is policing the area he lives in so they have family, friends and tribal leaders coming up to them and asking them to turn a blind-eye when they are moving a poppy crop through a checkpoint - that happens quite a bit."

"But sometimes there is an insurgent who could be known to the policeman who will ask him to turn a blind-eye so he can carry out whatever he intends to carry out. We know this and we've monitored this in some occasions. It's not because the policemen is aligned to the insurgency, it's not because he is a Taliban who has joined the police, it is because of these external influences against him from his family, from his tribe.
Link:http://www.bbc.co.uk/news/uk-19672852