Victoria's deputy opposition leader believes it was untenable for a Liberal MP to remain in the party after she had confirmed plans to sue the leader.
David Southwick on Wednesday told the Federal Court the Liberals were left with no other option than to expel Moira Deeming from the party in May 2023.
He said she had briefed journalists with her plans to sue Victorian Opposition Leader John Pesutto, which was unacceptable.
"There were colleagues that felt infuriated that the leader was being threatened," Mr Southwick told the court on day 12 of Mrs Deeming's defamation trial against Mr Pesutto.
She alleges he defamed her by suggesting or implying she was a Nazi in comments he made following a Let Women Speak rally.
The March 18, 2023, event was gatecrashed by neo-Nazis who performed the Nazi salute on the steps of state parliament.
Mr Pesutto has denied any wrongdoing.
Mrs Deeming first received a nine-month suspension on March 27, 2023, with a party-issued statement stating she accepted it might have been an "error of judgment" to go to the rally.
Mr Southwick said he met with Mrs Deeming in late April where they discussed plans for Mr Pesutto to issue his own statement denying Mrs Deeming was a Nazi sympathiser.
But Mr Southwick said Mrs Deeming briefed the media of her plans to sue Mr Pesutto so the "deal was off".
"She was never prepared to work through what we were trying to do in good faith," Mr Southwick told the court.
He maintained Liberal partyroom members pushed the motion to expel, rather than the leadership team.
"People were lining up to put their name on the motion," he said.
Mr Southwick was also grilled on his decision to secretly record a meeting with Mrs Deeming and the Liberal leadership team on the day after the rally.
In the 70-minute recording played to the court, Mrs Deeming was criticised for her involvement in the rally and for photos showing her having champagne afterwards with fellow organisers.
She is also heard telling the leaders she did not realise the Nazis were even at the rally and she did not support them.
Mr Southwick told the court he spoke to Mrs Deeming on the day of the rally and instructed her to issue a public statement condemning the Nazis.
He claims she instead sent out a tweet saying she was disappointed police had walked "masked men" past the rally as they did a "horrible Nazi salute".
Mr Southwick told the court she should have been stronger in calling them Nazis and denouncing what had been "one of the darkest days" in Victoria.
The deputy leader said he chose to record the next day's meeting because he could not trust Mrs Deeming and he needed to protect himself and the Liberal Party from what was about to happen.
"I wanted to make sure the whole events weren't turned around and misconstrued," Mr Southwick told the court.
"For me, it was an insurance policy."
The recording was uncovered a week before the trial started and Mr Southwick maintained he never intended for anyone to hear it.
The other members of the meeting did not know he was recording it on his iPhone, Mr Southwick said.
But he admitted he told Mr Pesutto about the recording in November or December 2023, once it became clear the defamation case might proceed to court.
Mr Southwick denied he withheld the tape because it contradicted the statements of Mr Pesutto and other members of the Liberal leadership.
He also claimed he did not listen to the recording before making his written statement, telling the court he felt his memory was sufficient to recall what had happened.
The defamation trial continues on Thursday.
