Simon Bridges' deputy chief of staff and former Chief Families Commissioner Belinda Milnes will on Thursday face assault and wilful trespass charges in the Masterton District Court.
Milnes is also the sister of National's finance spokeswoman Amy Adams.
In a statement, Milnes said: "These allegations are in the context of a bitter relationship break-up with my ex-husband. I will be vigorously defending the charges which are baseless."
Her lawyer Phil Mitchell said his client faces a charge of "technical assault" under the Summary Offences Act "in that the police do not allege she has touched anyone".
The trespass charge relates to a property his client has an interest in and, he says, "is similarly thin".
Milne's ex husband, David Ware, said he did not want to comment.
"The issue is I have two teenage daughters and I don't think it is particularly helpful for them to read about their mother in the press," he told the Herald.
Ware founded the listed telecommunications company TeamTalk 25 years ago but resigned two years ago as managing director, acknowledging at the time his behaviour had been "sub optimal" and had had attracted complaints from some of his 200 staff.
"I have been under huge stress for the past few years running three companies, commuting between Auckland, Wellington and Timaru while facing a challenging market situation and my health has gone downhill," Ware said at the time. "I haven't handled relationships well and the stress has taken a toll, so I'm heading to the farm to watch the grass grow."
Bridges and National's Deputy leader Paula Bennett both declined to comment.
Milnes is a close confidante and longtime advisor of Bennett's. She was appointed by her to the Families Commission in 2012 which sparked allegations of cronyism from Labour.
Bennett, at the time, defended Milnes' appointment, saying she was the right person for the job.
After just four months in the job she became the interim chief commissioner, taking over the role six months later.
The Commission was about to undergo a significant restructure to turn it into a research unit.
She resigned suddenly two years later to again work in Bennett's office and stayed there during her time as Deputy Prime Minister.
Milnes was appointed as second in charge in the National Leader's office after it lost its bid to become the Government.
Hosting a family violence conference in 2013, Milnes told delegates the Commission runs the annual White Ribbon campaign to raise awareness with men about domestic violence.
Milnes has a property in the Wairarapa and also a home in Wellington.