IT'S the wall-punching episode Tony Abbott insists "never happened" but now another mystery witness has emerged claiming the Liberal leader did try and intimidate university rival Barbara Ramjan.

The saga of whether Mr Abbott punched the wall on either side of Ms Ramjan's head prompted a strong denial from Mr Abbott when they first emerged.

But the allegations are backed up today in journalist David Marr's new extended book version of his Quarterly Essay: Political Animal by a mystery man claiming to be a witness.

"Suddenly a flying squad of yahoos led by Abbott came down the stairs. Abbott is unmistakable," the man said.

"Everybody knew Tony Abbott. He was all over campus all the time. He walked past me quickly but his gang screamed 'commie' and 'poofter' and the guy behind him grabbed me by the shoulders and threw me against the wall. I was furious. I picked myself up and immediately followed these thugs down the corridor.

"I saw Abbott raise his elbow above his head and his fist was clenched and then he drove his fist down. I did not see a punch land. As I pushed along the corridor, I saw Barbara being helped up very ashen-faced."

The biomedical professor, who asked not to be named, now insists he saw it happen July 28, 1977, only two days after the birth of the child Mr Abbott thought was his son conceived with a university girlfriend. Years later the child was revealed to be the son of another man.

Ms Ramjan is suing Nationwide News, the publisher of The Australian newspaper over claims Liberal Party powerbroker Michael Kroger made in an article that the Supreme Court has been told conveyed imputations that she was a serial manufacturer of false complaints against her political opponents and that she had fabricated an allegation that Tony Abbott had physically intimidated her in 1977.

Ms Ramjan's then campaign manager David Patch, now a Sydney Barrister who also says: "She told me that Abbott had come up to her, put his face in her face, and punched the wall on either side of her head."

The new edition also quotes Mr Abbott's letters to BA Santamaria in 1987 discussing joining the Liberal Party complaining that: "To join either existing party involves holding ones nose.

"The Liberal Party was divided between surviving trendies and the more or less simple-minded advocates of the free market," Mr Abbott writes.

He was ultimately encouraged to join the Liberals, rather than the Labor Party, by BA Santamaria.