He added: "It's part of the Abbott story - it is not part of the Abbott present." The incident will appear in a book on Mr Abbott and Labor leader Mark Latham to be published next month.

Mr Abbott said the case in January 1978 was dismissed. The magistrate complained of "enormous conflict" between the prosecution and defence evidence. The alleged assault was a "put-up job" staged by political opponents, Mr Abbott said - "to be embarrassing. And it was embarrassing." The case was published in Sydney's The Daily Telegraph in January 1978 on two successive days.

Helen Elizabeth Wilson, whose age was given as 29, a former student teacher, claimed she was assaulted in October 1977 when she was addressing students at Ku-ring-gai College of Advanced Education in a debate about whether the college should withdraw from the Australian Union of Students (AUS). She told the North Sydney court that someone had called out: "Why don't you smile, honey?" Then a youth had touched her on the upper part of her leg.

Mr Abbott, then 20, pleaded not guilty. The Daily Telegraph report said: "Miss Wilson said as she approached the microphone . . . two youths moved up behind her. "She said: 'I had just commenced speaking when I felt a hand between my legs on my lower buttocks. I was wearing jeans. I jumped back, turned around, and saw Tony Abbott laughing about two feet away. The people in the audience began laughing and jeering', Miss Wilson said."

Questioned by Mr Abbott's lawyer, the woman, who said she was the editor of two student newspapers, denied she was a women's activist. "She also denied having brought the charge against Abbott because he was a student leader with political views which clashed with hers," The Daily Telegraph report said.

Mr Abbott, who was in his third year of economics and law studies, told the court he had been asked to the college to support withdrawal from the AUS. "Abbott said: 'She was speaking about me in a highly critical way, calling me an AUS basher and noted right-wing supporter'," The Daily Telegraph reported. "'To let her know I was standing behind her I leaned forward and tapped her on the back, about the level of her jeans belt. I just wanted to attract her attention'."

Seven witnesses said they saw Mr Abbott touch Ms Wilson on the back. Outside the court Mr Abbott said the woman's evidence was "politically motivated". He threatened to consider action for malicious prosecution.

Mr Abbott has had wide publicity over fathering an illegitimate child while he was a student. His son was adopted out. He told The Sun-Herald he had alerted author Michael Duffy to the allegation for his frank Latham And Abbott book, which will be published by Random House next month. Ms Wilson declined to comment on the case when approached by The Sun-Herald.

This was one of two court appearances for Mr Abbott at Sydney University. In celebrations after passing his final year economics examination, he was challenged to bend a street sign. As he did so two policemen spotted him.

The offence was proven but no conviction was recorded. The matter hasn't come out until now. Mr Abbott said he had also told Duffy of this incident.