Police Commissioner Karl O'Callaghan said it felt like "a kick in the guts" to learn his "friend" and colleague WA Police executive director Greg Italiano had secretly referred him to the Corruption and Crime Commission.
The CCC cleared Mr O'Callaghan of any misconduct over the use of his corporate credit card, although it made adverse findings in relation to his spending and mix of business and personal travel.
The independent investigator instead found failings in administrative processes and rules surrounding corporate credit card use and overseas travel by public sector employees.
The CCC raised concerns over the use of corporate credit cards by all state employees and recommended strenthening the processes.
The Commission scrutinised receipts incurred by Mr O'Callaghan during two official trips to Broome last year, in January and October.
Mr O'Callaghan was questioned over whether he lied about police officer colleagues attending a dinner with him when in fact his wife attended.
While he later repaid his wife's share of the bill, it was not done for five months, well beyond the 25-day limit.
In October he used his corporate credit card to pay $3995 for accommodation at Pearle of Cable Beach, which the CCC found was "unusually high" compared to previous expenses.
The accommodation was booked for four adults and two children.
The CCC investigation found the accommodation had originally been booked for two colleagues to share with Mr O'Callaghan but they were later unable to attend and the hotel would not refund or cancel the room.
The CCC also raised concerns over the Commissioner's overseas travel, particularly a lack of distinction between private and official components of the travel, and visits to locations not included in the original itinerary.
In 2008 he and his wife travelled to Europe. While Mr O'Callaghan attended several official events the CCC found much of the trip was personal and had not been properly identified by the Commissioner.
"I do have concerns that a small sample of the business related travel undertaken by the Commissioner has lacked sufficient substance in respect of the original justification, the scope and nature of the activities taken on the journey and the follow up actions that flow as a consequence of the travel," WA Police executive director Greg Italiano told the commission during hearings.
CCC Commissioner Roger Macknay said WA Police corporate credit card practices were "cause for concern".
He recommended a review of the Treasurer's corporate credit card guidelines and that WA Police consider prohibiting use of the cards for personal circumstances and implementing sanctions for non-compliance.
The report says a position within the police service needs to be appointed to approve Flexi Purchase Account Statements when cards are used for personal expenses.
The CCC also recommends a review of guidelines for interstate and overseas travel by public sector employees.
Tabling the report in State Parliament today, Premier Colin Barnett said he supported all of the CCC's recommendations.
He said the findings left no substantial impediment to reappointing Mr O'Callaghan as Commissioner. Although his contract expires in a week, Mr Barnett did not confirm the Commissioner's reappointment.
The Premier consulted the Public Sector Commissioner, who said the corporate credit card practices and procedures did not reflect best practice and needed to be improved.