He acknowledged Coffey was very good at promoting te reo.
Sir Toby said any increase in te reo in mainstream media, whatever the percentage, would be beneficial for the language.
"For 176 years our country has managed to suppress it [in] schools and the consequences have been dire on our Maori learners. The quicker people are taught Maori the better it will be and that includes reading it, seeing it on television or listening to it on the radio."
Te Tatou o Te Arawa chairman Te Taru White said he thought the idea was a positive one.
"If it helps to revitalise and re-energise the language then it's a good thing," White said.
He believed 20 per cent to be a challenging figure. "But good for him if he can get there."
Included in Coffey's social media post was feedback from a viewer of the Moving Out With Tamati programme, which he hosted, saying how much they enjoyed hearing both English and Maori spoken during the episodes.
Coffey said about 10 per cent of the show was in Maori.
"I guess my TV show is living proof there is another way, which is not pushing it off to Maori Television and having it on mainstream, and actually putting a target or [quota] on it," Coffey said.
"While there has been much debate about whether te reo Maori should be compulsory in schools, ensuring it is spoken on television will mean many Kiwis can passively learn the language."
He added it was sad some New Zealanders might not like hearing Maori when watching television.
Television and radio host Stacey Morrison said she understood Coffey was working on details before forming a bill.
"It's best I wait to see his full proposal before saying anything," Morrison said.
Coffey said he would take into account further feedback, do research and talk to his colleagues before deciding on whether to draft legislation. "I know I have homework to do."
Any MP can propose a members' bill, unless they are a minister. To progress further the bill has to be drawn from the lottery of the ballot system. Government MPs who have a bill drawn have a good chance of seeing it become law.
Coffey posted feedback from a viewer of the
Moving Out With Tamati
programme, which he hosted, saying how much they enjoyed hearing both English and Maori spoken during the programmes.
NZ On Air funds a wide range of TV programmes, documentaries and shows, including Westside, Filthy Rich, Jono And Ben and Country Calendar.
The funding agency's website says it encourages the use of te reo Maori in mainstream content "as appropriate, to normalise the language as an official language of New Zealand". However, there is currently no target.
Te Mangai Paho, part of the Ministry of Maori Development, promotes Maori language and culture by funding broadcasting and production.
Last week Dunedin South MP Clare Curran was named the new Minister for Broadcasting, Communications and Digital Media.
Labour's stated broadcasting policy is to overhaul Radio NZ into RNZ+, which it says will be a "multi-platform provider dedicated to quality New Zealand programming and journalism".
An extra $38 million a year to fund New Zealand programming and journalism will be apportioned between RNZ+ and NZ On Air. Labour has said NZ On Air's general mandate and role will not change, but its charter and scope will be reviewed.
