Winston Peters says the National Party put him in a "similar situation" to Jami-Lee Ross, who was sectioned under the Mental Health Act last week.
Mr Ross was voted out of the National Party after being blamed for leaking Simon Bridges' expenses to Newshub.
He has also been accused by multiple women of harassment, bullying and using "brutal sex" to get compromising information - although it's been alleged the National Party leadership was involved in the women's decision to speak out.
Mr Peters says he has also suffered from serious attacks while a member of the National Party, which led him to resign from the party in 1993.
"The circumstances in which he found himself... is one of enormous stress and tension," he told RadioLIVE on Tuesday.
"I know something about it, because in a similar situation when I was in the National Party making speeches about the economic direction of the country and being pilloried by the leader of the National Party and my caucus colleagues, who were saying I was being disloyal to the party.
"I can tell you, it's an enormously stressful and difficult time, and you really have to steel yourself in order to take it if you're going to get through that experience."
The Mental Health Foundation says it is "disappointed" at some of the attitudes towards mental illness in recent discussions about Mr Ross.
"We believe you can have discussions about these valid issues without using discriminatory or stigmatising language and without weaponising Mr Ross's distress against him," it says.
Mr Peters says he is sympathetic to those with mental health problems, and hopes it raises public awareness of the issue.
"Families where it doesn't affect them are very lucky families," he says. "It should be treated like a physical illness, but it's not.
"I suppose if there's going to be something hopefully good out of all of this, in what was a total meltdown period in New Zealand politics, I hope that we better advance that sort of a public understanding."