BRUSSELS—Belgian police delayed a raid in the search for Paris terror attacks suspect Salah Abdeslam last month because of a legal ban on conducting them at night, the federal prosecutor’s office said Wednesday.

The acknowledgment could further fuel controversy over Belgium’s handing of the investigation into the Paris attacks. The country has been under increased pressure, notably by France, over its anti-terrorism policies and its failed attempts to catch Mr. Abdeslam.

Belgian...