Judith Collins says few in the National Party knew about the extent of Jami-Lee Ross' alleged bullying behaviour.
RNZ reported on Thursday evening a "gentleman's agreement" was reached two years ago between a woman who complained to the party hierarchy about Mr Ross and National Party president Peter Goodfellow.
And Katrina Bungard, the National Party candidate for Manurewa last year, told NZME she had been bullied by Mr Ross in 2016 and 2017 while on the Howick Local Board.
Simon Bridges - who became party leader earlier this year - has maintained he only found out about the alleged complaints in recent weeks, following the launch of the expenses leak inquiry. When Mr Ross went on leave earlier this month for "personal" reasons, Mr Bridges said it "came out of the blue".
Questions are now being raised why Mr Ross was allowed to rise up the National Party rankings over the past couple of years - becoming senior whip in 2017 - if the party knew of the allegations.
Ms Collins told The AM Show on Friday no one knew the whole story.
"I don't think anybody knew the full extent of all this," she told host Duncan Garner.
"And I think lots of people this week have been saying, 'Oh my goodness,' and words to that effect, and a few other words, as more and more revelations have come out.
"I think too everyone's busy at work. They're just getting on doing their things, and they're rushing from one meeting to the other and select committees and the House, and no one's really sitting around saying, 'Let's all put everyone's stories together.'"
Ms Collins said the only complaint she was aware of was Mr Ross' alleged bullying of Ms Bungard. She said it was "not of a sexual nature" but she didn't know the details.
As for claims Mr Ross has had a number of affairs, Ms Collins says she has heard "all sorts of rumours", but wouldn't say if any of them had involved another MP.
"You've got to be very careful on that sort of thing because there are other people involved obviously. I just think, you know, I'd rather not know definitely anything about that... Way more than we want to know."
Mr Bridges' job as leader looks safer now than it did on Tuesday, when Mr Ross claimed he had evidence the leader had broken the law. Nothing he's provided publicly since then has proven that, legal experts say, but it's not clear if Mr Ross has provided additional evidence to the police backing his allegations.
Ms Collins said without the inquiry into who leaked Mr Bridges' expenses, they would never have known about Mr Ross' alleged activities.
"We would still have someone not only leaking from our caucus and about us, but also someone who's clearly been acting very inappropriately from a position of some power."
Asked if Mr Bridges would step down if National's polling fell into the 30s, Ms Collins said she didn't know.
"What I would say is that when Jacinda Ardern became Prime Minister last year, her polling at the election was about 36 percent."
The difference being Labour have the Greens on-side, and it appears increasingly unlikely NZ First leader Winston Peters will ever do a deal with his former party National ever again.