Dennis Cliche has apologised for his "inappropriate" remarks. Credit:Jessica Hromas Fairfax Media last week revealed that Mr Cliche told the conference that in relation to the widened section of the M4 motorway that is stage one of WestConnex, "the day we turned on the tap and started collecting tolls was very exciting for us". Mr Cliche joked about gases from exhaust ventilation stacks that "kill the community" and stated "I would have no problem living underneath one". He then claimed the NSW Chief Scientist had been "extremely complimentary" about the stacks in a report to the Planning Department. "We do a huge amount of modelling and air studies and I won't quote, but the submission from the Chief Scientist of NSW was extremely complimentary on the [environmental impact statement] work we had done on our ventilation facilities," Mr Cliche said.

However, Fairfax Media has confirmed that Professor O'Kane wrote to Mr Cliche shortly afterwards to express alarm at the remark. It is understood that Professor O'Kane's letter branded the comments "false and misleading" and calling into question her integrity and independence as Chief Scientist and Engineer. The letter is also believed to have warned that the remarks risked undermining community confidence in the process by which the Advisory Committee on Tunnel Air Quality, which Professor O'Kane chairs, reviews WestConnex and other tunnel projects. Professor O'Kane told Fairfax Media that she had decided to commission one expert advisory committee member, Dr Ian Longley, and an external Swedish expert, Ake Sjodin, to write the report. She said this was a process she had undertaken on previous occasions to ensure the best possible independent expert advice. "I wrote to Dennis and told him 'I want this sorted out'," she said. "I did it because I was really concerned that the public knows the process, because we'd put so much effort into it. We deliberately went to people who are respected in the international community." Professor O'Kane agreed to the wording of a letter to The Sydney Morning Herald in which Mr Cliche said his remarks at the conference were "inappropriate and I apologise for them".

"I'd also like to clarify that the review of any major tunnel EIS is conducted by non-conflicted members of the NSW government's Advisory Committee for Tunnel Air Quality and international experts, independent of NSW Chief Scientist and Engineer Mary O'Kane," he wrote. Opposition transport spokeswoman Jodi McKay said Mr Cliche "is fast running out of people to apologise to". "He's already offended residents along the corridor who might be living under smokestacks and western Sydney motorists who are paying $2,000 a year in tolls. Now he's been forced to clarify the Chief Scientist's role," she said. A spokeswoman for Sydney Motorway Corporation said it had "nothing further to add".