Irregular expenditure in North West municipalities has increased from R3,19 billion to R4,29 billion in the 2016-17 financial year, the Auditor General said on Thursday.

"The three municipalities that contributed to 55 percent in this regard were Rustenburg local municipality with R983,5 million, the Ngaka Modiri Molema District Municipality with R827,8 million, and Madibeng local municipality with R561,9 million," Success Maroto, business executive responsible for the North West province said.

He said 17 municipalities were qualified due to disclosed irregular expenditure being either misstated or incomplete.

"This means that it is probable that a large portion of irregular expenditure may be uncovered and still be disclosed in the future."

Mahikeng municipality was the only municipality in North West with an improved audit outcome, from a disclaimer of opinion to a qualified opinion with findings.

Four municipalities regressed from unqualified with findings to qualified with findings. Twenty of the 22 municipalities in North West had an undesirable audit outcome.