A Hamilton-area MPP questioned a staffer's commitment to his job after he took parental leave to care for his baby, shows a voicemail obtained by CBC News.

In that same call, the Ontario NDP's Paul Miller also suggests the union representing party employees does "more harm than good."

Miller, who represents Hamilton East–Stoney Creek, complained in the October 2016 voicemail to constituency assistant Todd White that he'd barely communicated with the office during his 10 months on parental leave.

White had recently returned to work when, according to a complaint filed last month with Human Rights Tribunal of Ontario, he was suspended, partly because he chose not to work optional overtime.

"I probably didn't hear from you … maybe once in 10 months?" Miller says in the voicemail. "It doesn't give me a feeling of interest in your job. It doesn't give me a feeling that you care about the office. It doesn't give me a feeling that you're loyal.

"What I'm trying to tell you is there's going to be big changes real quick in the next few months, or it's going to be an ugly situation."

The recording, a portion of the voicemail, runs almost three minutes.

Miller takes also aim at the Canadian Office and Professional Employees Union (COPE), which represents NDP workers.

"I could write a book on all the other MPPs that are having problems too, and it's just with COPE," he says in the recording.

"Sometimes unions do more harm than good, and sometimes, they get their people into bad situations."

Wade Poziomka, White's lawyer, called the comments "inappropriate."

"There is no room for these antiquated views in the modern workplace," he said.

It is the latest chapter in an ongoing battle between Miller and White, who says the MPP started discriminating against him when he went on leave.

White is also chair of the Hamilton-Wentworth District School Board.

Miller, who was first elected in 2007, is up for re-election in the June 7 provincial election.

In his complaint, White says he worked in Miller's office for eight years with few issues. Then, in 2015, he took parental leave to be the primary caregiver for his baby. His wife, a doctor, is self employed and couldn't take time off.

Miller, who represents Hamilton East–Stoney Creek, is up for re-election on June 7. (Ontario NDP)

White, who is on parental leave for his second child now, alleges Miller has used "discrimination, defamation" and "breaches of privacy" to pressure him to leave. He also claims Miller routinely made sexist, racist and homophobic comments around the office, and pressured employees to campaign for him during office hours.

In a statement issued through the party, Miller said he'd been frustrated with White's job performances, and told him so a number of times, including through his caucus and the union.

"These frustrations and concerns are now the subject of the grievances currently subject to arbitration," he said. "I am confident that the process will resolve fairly, and demonstrate that I acted reasonably, in good faith, and consistent with my obligations under the collective agreement."

Marla DiCandia, caucus director of operations, said the party won't talk about specific personnel issues.

"We are proud to be the only unionized caucus in Ontario," she said. "We value our staff collective agreements, and the grievance and arbitration processes they lay out.

"We are committed to working with our staff unions to resolve all disputes in a fair, transparent and credible way consistent with the terms of their agreements."

Gary Howe, president of the United Steelworkers Union Local 1005, wrote a letter to the media in support of Miller on Thursday.

"Paul has fought for workers' rights for as long as I've known him," Howe said of Miller, a former steelworker. Miller, he said, has "helped many people."

"Paul has fought for pension security for workers in Ontario for at least 10 years, and has put in private member's bills to try and help Ontarians living in poverty."

The complaints come as Ontario NDP Leader Andrea Horwath, also a Hamilton MPP, hopes to pull ahead of the Liberals and Tories in the provincial election. (Chris Young/Canadian Press)

Last week, Ontario NDP Leader Andrea Horwath said the complaints are proof the system is working.

Unionization is "protection for those workers to make sure when something occurs that they have a remedy," she said. "That's what's going on right now."

The Miller and White conflict isn't the only one in local NDP offices. Two employees of Hamilton MPP Monique Taylor — Alissa Watt and Sandra Troulinos — have also filed human rights complaints.

Both Watt and White say they haven't been contacted by NDP human resources staff. The party wouldn't comment on that Thursday.

CBC News is pursuing comment from COPE.