The report by the head of Mr Barnett’s own Department of Premier and Cabinet found Mr Nalder’s numerous shareholdings and business links — which he had failed to fully declare after becoming a minister in March — had created multiple conflicts of interest.

Mr Nalder, a businessman who was once seen as the rising star of the Liberal Party and a potential successor to Mr Barnett, was this week stripped of the finance portfolio but managed to retain transport.

On Monday Mr Barnett said Mr Nalder had made “serious errors of judgment” in mixing his private and public roles but there had been no “actual” conflicts of interest and he would remain in Cabinet.

However, the Premier today released a memorandum written by his department secretary, Peter Conran, that highlighted the extent of Mr Nalder’s real and perceived conflicts of interest and breaches of the ministerial code.

The report found that Mr Nalder had breached the code by attending a meeting in August with the Chinese Consul-General in Perth along with Darryl Ashworth, the chief executive of Metier Asia, a company in which Mr Nalder and his wife have a major shareholding.

Mr Conran said Mr Nalder’s office had invited Mr Ashworth to the meeting, which was an error of judgment and failed to adhere to the code of conduct.

“The Minister maintains he was inviting Mr Ashworth for his expertise in the subject matter under discussion but he should have identified the very real risk of a perceived conflict of interest that he was mixing a private investment partner with his public role,’ the report said.

Another attendee at the meeting was Mr Nalder’s ministerial policy adviser, Sarah Boska, who was also a shareholder in Metier Asia. Mr Conran found this also breached the code of conduct.

The report found that Mr Nalder’s close personal and business links with Alan Ariti, a senior executive at IT company Amcom, had created an “actual conflict of interest “ given the Minister’s responsibility for IT matters within government.

Mr Nalder had made an “error of judgment” in hosting a lunch for Mr Ariti — a fellow investor in several companies including Amcom — at Perth’s Weld Club this year along with his staffers and an officer from the Department of Finance.

Mr Nalder and Mr Ariti discussed ways to achieve reform of IT issues in the government.

The Department of Finance officer who attended was Mr Nalder’s first cousin. “This was again an error of judgment by the Minister,” the report said.

After the report was released, Mr Nalder said believed he had acted with honesty and integrity and had not committed any wrongdoing.

He said he invited his cousin to the meeting because he had a high level of expertise in IT.

“I have made mistakes and I am learning from the experience, but those mistakes are around the creation of a perception that I may have done something wrong rather than actually doing something wrong,” he said.

Mr Nalder said he believed there was a campaign against him.

“This seems to be a targeted campaign to smear my name,” he said.

In the report, Mr Conran laid some of the blame for Mr Nalder’s conflicts on his own department. He said he had not pursued Mr Nalder “in a sufficiently aggressive manner to obtain the full details of his business interests”

But Mr Conran said the code also requires ministers to fully disclose all business interests, which Mr Nalder had not done.

“It is noted that the Minister did not provide the details such as his relationships with other directors and their business links that would have assisted the department’s assessment of his declaration,” he said.

“This certainly hampered my and this department’s ability to provide advice to the Minister on managing his conflict of interest.”