Troy Buswell, the leader of the opposition Liberal Party in Western Australia, was under intense pressure to resign over the incident, which happened in 2005.
He dismissed allegations on 13 different occasions that he had sniffed the seat, before finally admitting yesterday that it had in fact taken place.
“All I can confirm is that the events described in the paper [The West Australian] by the former female staffer are accurate,” he said.
Holding back tears at a news conference, Mr Buswell admitted that his behaviour before becoming party leader three months ago had sometimes been highly offensive.
He has previously admitted to snapping a woman’s bra as a drunken party trick and has been accused by a retiring Liberal MP of making sexist remarks to her.
The emergence of the chair-sniffing incident had placed a strain on his marriage, he conceded.
“These are difficult issues for me to deal with and they are very difficult issues for my family to deal with,” he said.
“It’s hard dealing with these matters and having to face up to your responsibilities behaviourally, publicly, and it’s harder to do it privately.”
Mr Buswell’s deputy, Kim Hames, stood by him, describing him as a rough diamond with a robust sense of humour.
“To me, Troy’s a rough diamond and you don’t fix a rough diamond by smashing it to pieces,” said Dr Hames.
“You take those rough edges off and you’ve got something that is of quality, and I think Troy is a quality person, and when you get to know him and know what he’s like, these incidents aren’t what he’s like.”
Other members of the Liberal party said privately they were disgusted by the whole episode, but would not challenge Mr Buswell as leader of the Liberals because there was no better candidate.
The woman at the centre of the row, who wants to remain anonymous, said the seat-sniffing saga happened at Mr Buswell’s office in the Western Australian state parliament.
The MP had done it to get a laugh from colleagues, she claimed. “I was shocked and outraged and I told him,” she said.