Rory Amon, 36, returned to the witness box on Monday to defend a slew of child sex charges relating to the teen in 2017.
The boy, who was 13 years old at the time, met the future politician through a gay dating app before the alleged rape and sexual abuse took place.
Amon says he drove to the teen's Sydney apartment on July 22, 2017, believing the youth was 17.
This claim was tested under sometimes-heated questioning by crown prosecutor Meaghan Fleeton on Monday.
"He told you, in fact, he was 15 and he told you possibly his real age even later?" she asked.
"No," Amon replied.
The ex-MP also denied photographs, sometimes explicit, sent by the teen on Snapchat showed his true age.
Amon had seen the teen under street lights and then in the lit bathroom before the light was turned off, Ms Fleeton said.
It would have been obvious that the youth was under 16, she suggested.
"He told me he was 17 and nothing I saw changed that belief," Amon answered.
The former MP admitted using fake names on Grindr and to register the phone on which he installed the dating app.
The names were there to prevent his sexuality coming out, derailing his political career and affecting his private life, he told the NSW Supreme Court jury.
"You would agree that private life involved secretly having sexual intercourse with a 13-year-old," Ms Fleeton asked.
"No," he responded.
He rebuffed crown suggestions he had tailored his evidence.
Amon claimed to remember talking about ages while being vague around other aspects of the alleged meet-ups, Ms Fleeton said.
The complainant - who can't legally be named - said he first chatted to Amon on another hook-up website, Squirt.
The former MP said he agreed to meet the boy outside a Sydney unit complex before being led to the underground car park's bathroom.
He was hazy on the details about what happened next but said he likely would have asked for a kiss.
His barrister, Matthew Johnston SC, repeated evidence the now 22-year-old complainant gave earlier in the trial about what happened between the pair.
The man said Amon guided his hand to his genitals before they had oral sex.
"I don't dispute that," the former MP said on Monday.
But Amon denied allegations he visited the teen's home a second time when the then-boy said further sexual acts took place.
On that occasion, the then-27-year-old allegedly brought a towel that he placed on the floor of the bathroom.
Ms Fleeton said Amon almost never looked his alleged victim in the eye while he gave evidence earlier in the trial.
But the ex-MP said he looked at him "from time to time" and didn't want to make him feel uncomfortable.
At the time of contacting the youth, Amon was working full-time for federal Mackellar MP Jason Falinski.
He would go on to serve two terms on Northern Beaches Council before being elected as the Liberal MP for the state seat of Pittwater in 2023.
In 2022, he reconnected with the alleged victim on Grindr, sending him a number of messages including a photograph of himself wearing volunteer firefighter attire.
The former MP has pleaded not guilty to 10 charges, including five counts of having sexual intercourse with a child and two counts of attempted sexual intercourse with a child.
He also denies indecent assault charges.
Closing submissions in the trial will start on Tuesday.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
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