Knowles' political career was damaged by allegations raised by nurse Nola Fraser in relation to deaths at Campbelltown and Camden hospitals when he was Minister for Health. An Independent Commission Against Corruption inquiry into Knowles' behaviour cleared the minister in September 2005, but he had already been moved from the health portfolio. He was also damaged by the Orange Grove affair, as a supporter of a retail outlet, which was later found to have been opened in contravention of zoning regulations in his electorate, while he was Minister for Urban Affairs and Planning. In April 2005, he was charged with drink-driving at a random breath test, with a low-level over the limit reading.