Opposition parties want an inquiry into the capacity schools have to teach te reo Maori.
The Greens and NZ First are going to ask Parliament's education and science select committee to conduct it.
They say the last two censuses show the proportion of Maori who speak te reo dropped from 25.2 percent in 2001 to 21.3 percent in 2013.
"The guidelines for English medium schools to teach te reo are voluntary and the commitment is variable," Green's Catherine Delahunty said today.
NZ First's Tracey Martin says there needs to be an assessment on the capacity of schools to deliver.
They're required to teach a language, but not necessarily te reo.
"We need to treat te reo as the taonga that it is," she said.
"Politicians now need to lead in a cross-party consensus that te reo must be well resourced and supported in all schools."
Ms Delahunty and Ms Martin will ask the committee on Wednesday to agree to carry out the inquiry.
Maori language week started on Monday and Maori Development Minister Te Ururoa Flavell wants a greater focus on the language all year round.
Mr Flavell, who is a co-leader of the Maori Party, says even though there have been huge gains, it will be "back to the normal habits" once Maori language week is over.
He doesn't think New Zealanders are doing well enough when it comes to pronouncing Maori words - whether it is someone's name, the name of a street or suburb, or even Aotearoa itself.
"It's a wonderful language that we should be proud of, and people should take it up in a far more fervent way," Mr Flavell told reporters.
"Until we shake the tree a bit and make it an issue for all New Zealanders by pointing it out, sure it might take people back a bit, but at least it's got everybody to think about it."
Te reo Maori is one of New Zealand's three official languages - the other two being English and New Zealand sign language.