New Delhi, July 17: Delhi chief minister Arvind Kejriwal today described the capital's police as thulla, a common Hindi slang for "cop", and sparked a row.

"These people want that even if a thulla is caught demanding money from street vendors, we can't try him," Kejriwal said during a television interview when asked about his row with Delhi police over control of the anti-corruption branch.

The police were not amused.

Buttonholed by TV crews, police commissioner B.S. Bassi said: "I refuse to believe the chief minister could have used such a word. But if he has, it is very unfortunate and derogatory."

Leader of the Opposition, the BJP's Vijender Gupta, demanded an apology. "Kejriwal has become an expert in using unparliamentarily language for cheap publicity. He must apologise for demoralising Delhi police and lowering their dignity."

Thulla is used to stereotype a cop as a slow-moving constable with a big belly. Its etymology is not clear but it is the stuff of police lore that the word comes from "thoolah" or jute sacks whose colour is similar to the police's khaki.

Mama, the equivalent of thulla in the east and the south, has also found its way into popular culture. In the 2012 biopic on athlete and later Chambal dacoit Paan Singh Tomar, played by Irrfan Khan, the song Mamaiya kero kero Mama accompanies sequences of gun battles and flight from the police.