More than 65,000 Afghans have been driven out of Pakistan since the start of the year after coming under intense scrutiny following a Taliban massacre of 150 people in December 2014 -- billed as Pakistan's "mini 9/11".
The refugees who remain are viewed with deep suspicion inside Pakistan and are routinely accused by authorities of harbouring militants.
"The Pakistani police's outrageous mistreatment of Afghans over the past year calls for an immediate government response," said Phelim Kine, deputy Asia director at Human Rights Watch, in a report entitled: "What Are You Doing Here?': Police Abuses against Afghans in Pakistan".
The report noted that in June, the federal minister for States and Frontier Regions, Abdul Qadir Baloch, announced that there would be no official reprisals against the country's Afghan population in response to the Peshawar attack.
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"Despite that promise, Pakistani police have pursued an unofficial policy of punitive retribution that has included raids on Afghan settlements; detention, harassment, and physical violence against Afghans; extortion; and demolition of Afghan homes," HRW said.
Such police abuses have prompted fearful Afghans to restrict their movements, leading to economic hardship and curtailing access to education and employment.
Deteriorating conditions in Afghanistan have already prompted more than 80,000 Afghans to leave their country in 2015 and seek asylum in Europe, according to the rights group.
Afghans uprooted by police abuses in Pakistan, where many have lived for decades, to return to Afghanistan may well add to the numbers of those seeking refuge in Europe as conditions deteriorate in Afghanistan, it added.
"The Pakistani government needs to develop a long-term strategy that emphasises the protection of its Afghan population rather than pursue a vindictive punishment policy that is as unlawful as it is inhumane," said Kline.