By Thomas Harding
The charity has warned that unless the international community acts immediately the country will not be secure enough to hand over to Afghan forces in 2014.
The report, titled No Time to Lose, claims Nato is not doing enough to prevent abuses by Afghan police and "time is running out" for change.
It warns that unless training is "urgently stepped up there is a serious risk that abuses and violations by Afghan forces will escalate".
As Nato prepares for withdraw from Afghanistan there are "serious concerns regarding the professionalism and accountability of the security forces they will leave behind".
Afghan police are committing crimes such as child sex abuse, torture and killings with impunity, said Oxfam on Tuesday, warning the violations could escalate as local forces take on frontline role. (Photo: AP)
It outlined a number of abuses that Afghan forces are alleged to have carried out including torture, killings and sexual abuse of children.
"Incidents of sexual abuse and exploitation of boys (including the practice of 'dancing boys') by the ANSF [Afghan National Security Forces] have also been reported, although the subject is so taboo that understanding the extent of the problem is difficult."
As greater responsibility is handed over to the Afghans the report warns there is a "serious risk" that human rights violations will escalate and civilians "will pay the price".
The civilian death toll of the conflict in Afghanistan is getting worse each year with 2,777 killed last year, about 10 per cent of them by security forces.
It gave an example of a girl killed by a soldier who the security forces helped flee the area. In another incident women were lashed in public by local elders as members of the police stood by "laughing and clapping".
There was no "satisfactory mechanism" for an individual can lodge a complaint against the security forces and people were scared to do so.
"There are serious concerns regarding the professionalism and accountability of the security forces that will be left behind."
The report said there are an estimated 40,000 police who have had no training at all and criticises Nato for prioritising quantity over quality.
Many people with "dubious human rights records" have been recruited particularly in the Afghan Local Police who act as local militia groups and have allegedly been involved in kidnappings and beatings. The report calls for further ALP recruiting to be suspended.
Rebecca Barber, who spent three months in Kabul compiling the report, said: "The Afghan people need to know these forces will protect them and be brought to justice if they commit abuses – or public trust and confidence in the government could be seriously undermined."
She said the British government was not giving enough details on the state of the police and added it needed to contribute more than the 14 police officers currently training Afghans as Finland had 37 and Germany 36.
Despite the reports criticisms there has been a marked improvement in the training and vetting of the police force in Helmand, especially following the incident in 2009 when five British soldiers were murdered by a rogue policeman.