Eleven, including Mr Shearer, have said they don't support it or are yet to be convinced.
Eleven refused to comment. Five said they were undecided and would make their call when the proposal was debated at the party's national conference in November.
While Mr Shearer yesterday said he "absolutely supported" having more women MPs in Parliament, "this mechanism in particular, I'm not supportive of".
Labour has a target of lifting the percentage of women in caucus to 45 by next year and 50 by 2017. About 41 per cent, or 14, of its present 34-strong caucus are women.
Mr Shearer said he wanted to reach the targets, "but the bottom line here is how we would do that".
"I don't like the idea that we are going to be enforcing something like that. I think we should be doing it as a matter of getting behind good women and making sure they get into Parliament.
"It's about making sure we get excellent candidates up and we select them. It's as simple as that."
Mr Jones said he had spent yesterday in and around Kerikeri and Kaitaia talking about the proposal, "and the overwhelming response is the public doesn't want the country run by geldings".
"Of course it's important that we have a diverse set of personalities in our caucus but merit cannot be disowned for mediocrity, whether it's Maoris, women or anyone else."
Mr Jones said most people in the provinces - where Labour needed to recapture support - were focused on the economy.
"They don't care who is going to exercise the power provided they're talented, they've got merit and they can develop a solution to the economic woes affecting so many people."
Christchurch Port Hills MP and former Labour president Ruth Dyson did not want to discuss the issue but her electorate committee chairman, James Dann, said she had strong views on the matter "and so she should".
"As it stands, it's almost as if the pay gap and things like that don't exist. People seem to think that feminism is a done deal, but it's not.
"And if a political party is not going to do anything about changing the gender balance within its own organisation then how do you expect it to do anything about progressing gender balance in society?"
The proposal was "not ideal but it's a good place to start", he said.
List MP and former party president Maryan Street said she opposed all forms of quotas in the selection process.
"When I was president and was writing the rules for list selection, I argued vehemently against quota and I have maintained that position and made it known within the party."
Ms Street said it was hard enough being a woman in Parliament without facing accusations of being there by way of gender.
"I think it's about competence. It's always about merit."
However, given the ongoing frustration for years within the party over the lack of gender balance in caucus, it was not surprising that proposals such as the one revealed this week were raised.
