During heated questioning on Thursday, McLachlan, 56, faced claims of colluding with his partner to make up stories for the court and giving conflicting evidence about whether he had touched or kissed certain actresses.
Under cross-examination, the Gold Logie award winner was grilled about whether he had actually kissed the body of the actress playing the character Janet during a bed scene in The Rocky Horror Show after he had disappeared under the bedsheets.
While McLachlan claimed he made "air kisses" under the sheets for comedy, defence barrister Michael Hodge QC accused him of making up the story.
"It's a deliberate lie," Mr Hodge said.
"No, it's not," McLachlan replied.
McLachlan is suing the ABC, Fairfax, and actress Christie Whelan Browne, 39, for defamation over publications in January 2018 relating to claims of misconduct during the 2014 production of The Rocky Horror Show and other productions.
McLachlan admitted "jokingly" kissing Whelan Browne once on the hips while underneath the bedsheets after scrambling to find his dropped prop e-cigarette.
He denied pulling back Whelan Browne's underwear and kissing her buttocks during that same scene, saying the move was physically and temporally impossible.
When saying that Whelan Browne had also worn a personal g-string and a second pair of underwear under her white stage knickers, Mr Hodge questioned how the actor had known this.
McLachlan admitted giving one Rocky Horror cast member, who cannot be named, a "quick playful peck" on the lips and kissing another actress, Erika Haynatz, 47, on the lips after saying he was infatuated with her and, in an impression of Jim Carrey from The Mask, said he had fallen in love with her.
The jury was told of a dressing room feud in which Whelan Browne was accused of relentlessly bullying Haynatz. McLachlan claimed he kissed Haynatz in her dressing room to comfort her while his partner Vanessa Scammell was in the theatre.
Mr Hodge accused both McLachlan and Scammell of concocting this story, pointing out that on the actor's own evidence, he had not actually said anything to Haynatz about the alleged bullying when he visited for the kiss.
In a clip played to the jury from a Spotlight interview given to Seven Network last May, McLachlan claims he had merely given a "greeting kiss" to Haynatz.
"You can see the absurdity of that explanation, can't you?" Mr Hodge said.
The actor has denied the allegations in the publications, and has accused Whelan Browne and two other women of approaching the media for notoriety or money.
