An internal email, listing prayer times, asked officers not to execute arrest warrants during those periods for reasons of religious sensitivity.
The Muslim holy month of Ramazan is due to end next week.
The message was sent to officers in the metropolitan division of the Greater Manchester Police (GMP) force which covers an area calls "one of the most diverse in the UK with a wide range of ethnic groups".
A police spokesman said that a second email had been sent making clear that there was no blanket ban on arrests, simply a request for sensitivity.
GMP said in a statement: "The month of Ramazan is an important time of the year for members of the Muslim community throughout the world.
"It is important that normal, planned policing activities and operations are maintained, while ensuring that officers are professional and respectful to members of the community while going about their duties."
A GMP spokesperson insisted that officers were not being told to refrain from arresting Muslims during Ramazan.
"If anyone, of any faith, commits a crime during Ramazan, they will be arrested," he said.
"We are concerned that reports that Muslims will not be arrested will inflame community tensions."
Some 9.1 percent of people in Manchester identified themselves as Muslims in the 2001 census. The figure is higher in some of the north-west English city's suburbs.

Copyright AFP (Agence France-Presse), 2006