"We are at a crisis point for the future of vocational education in New Zealand," Grey said.
"If we don't act soon, there will be very little left of the provision of vocational training of the type that the polytechnics do exceptionally well."
Enrolments at the country's 18 polytechnics and institutes of technology dropped by 11 per cent from 71,945 equivalent fulltime domestic students in 2012 to 64,280 last year, as the buoyant job market pulled many young people straight into work instead of training.
Funding, which is based on equivalent fulltime student numbers, has dropped too.
"All of our polytechnics are really struggling financially," Grey said.
Manukau's equivalent fulltime domestic enrolments plunged by 19 per cent, from 7035 in 2012 to 5715 last year.
Grey said Manukau cut 54 jobs in 2014 and 14 more last year before the latest proposal to cut faculty deans and associate deans, replacing them with managers of the Ōtara North, Ōtara South and Manukau campuses.
"It's a major restructuring from seven faculties down to three campuses," she said.
A Manukau Institute of Technology spokesman said the review was "focused on faculty leadership structures with the consultation period ending in mid-November".
"It is expected that the results of the process will be delivered in late November," he said.
"MIT is committed to its community and students with the review intended to create an organisation that can deliver the best outcomes for these groups in the future."
Grey is due to meet new Education Minister Chris Hipkins on Thursday and said she would seek "an urgent cross-sector meeting about the future of vocational education".
"It's about the political will," she said.
"The funding model for the last nine years has been the same for everyone. Maybe there is a different model needed for some of our communities. We need to get around a table and start talking about it."