National MP Matt Doocey is pushing for the Health Select Committee to open an inquiry into the 15 new Inpatient Mental Health Facilities and upgrade projects under development.
He's urging his fellow select committee members to vote in favour of his motion at Wednesday's meeting.
The call follows reports of overflowing facilities that are in poor condition.
The Health Minister Andrew Little himself has expressed frustration at the time taken to get shovels in the ground and wanted funding to roll-out faster.
The latest update from the minister is that, out of the $438.2 million set aside for facilities in Budget 2018 and 2019, only $24.9m has been spent and $13.6m has been reimbursed to DHBs.
Doocey said the current state of mental health inpatient facilities is unacceptable.
"Many of them have stained carpets, torn curtains, they're overcrowded, they have pests and vermin and they're damp.
"We wouldn't send people to a hospital with a broken leg to conditions like that, so why do we send people with mental health issues to those sort of environments?"
Doocey said it would be very concerning if the motion was voted down.
"We do know from Government and opposition parties, everyone has voiced their real concern and frustration at the building of these new mental health inpatient facilities.
"Everyone has agreed that we need to be building these at pace and everyone is very concerned about why it seems to be taking so long to get shovels in the ground," he said.
He said an inquiry would identify the roadblocks to getting facilities built.
"We can't manage something that we aren't measuring, so an inquiry is a way of understanding where each of those impatient facilities are at with their construction and understanding what we can do as a Parliament to help accelerate that," he said.