The Morrison government has ordered a national integrity watchdog to examine a string of allegations about the conduct of Commonwealth officials linked to Crown's casino operations.

Attorney-General Christian Porter told federal Parliament on Tuesday afternoon the allegations of the apparent cosy relationship between Crown and government agencies, including favourable visa processing in China, would be probed by the Australian Commission for Law Enforcement Integrity.

Mr Porter said it was important there was "public confidence" in the nation's law enforcement agencies, including immigration and customs, and "all allegations of illegal activity" were taken seriously.

"They hold very privileged positions and, as such, are expected to uphold the highest standards of integrity and professionalism at all times," Mr Porter said.