The police watchdog is investigating a complaint that a man received "degrading treatment" after he was arrested in Newcastle.
A 34-year-old man, who was arrested in December for being drunk and disorderly, has alleged officers used excessive force on him.
He also accused them of taking his clothes off, leaving him naked from the waist down.
The Independent Police Complaints Commission (IPCC) is investigating.
Northumbria Police said it was unable to comment while the investigation was ongoing.
IPCC Commissioner Nicholas Long said: "This man has made a serious allegation that he was subject to degrading treatment while in custody.
"It is important for the IPCC to provide independent oversight to the investigation and we will ensure the findings are published in due course."