Former South Australian deputy premier Vickie Chapman has been cleared of any conflict of interest in denying approval for a $40 million port project on Kangaroo Island where her family has property.
Ombudsman Wayne Lines said after taking evidence and visiting the island, he had determined that Ms Chapman had no perceived, potential or actual conflict in rejecting the Smith Bay proposal.
Mr Lines also cleared former premier Steven Marshall of maladministration in failing to determine if there was any substance to the allegations against his deputy.
"In the lead-up to Ms Chapman's determination of the Smith Bay application, she did not say or do anything that would suggest she was considering it on anything other than its merits," the ombudsman said.
"Her staff and legal advisers had no cause for concern that the decision-making process might be influenced by a conflict of interest."
The issue had been referred to Mr Lines last year, after a damning report from a parliamentary committee that heavily criticised Ms Chapman's handling of the port proposal.
As planning minister at the time, she had rejected the development on environmental grounds, despite her own department advising that it could go ahead subject to a number of conditions.
Ahead of the ombudsman's inquiry, Ms Chapman resigned as deputy premier and planning minister and stood aside as attorney-general.
However, she continued to deny any wrongdoing.
The ombudsman's finding was some good news for the now opposition backbencher as her status in the parliament remained unclear.
After only being returned at the March state election, Ms Chapman recently announced her decision to quit politics.
She had intended to officially resign from the parliament on May 31 and recently wrote to parliamentary Speaker Dan Cregan outlining her plans.
Mr Cregan advised her that, under the constitution, her resignation appeared to become effective from the date he received her letter late last month.
But in a statement during the first sitting of the new parliament on Tuesday, he said, based on the latest Crown law advice, the question of Ms Chapman's status would be left for the house to determine.