National has no plan to match the Green Party by setting a quota for women MPs or ministers, Deputy Prime Minister Bill English says.
Mr English was challenged in Parliament this afternoon to raise National's proportion of women ministers from 30 per cent to 50 per cent.
Earlier today, the Green Party announced that half of its Cabinet would be women if it entered Government.
Out of National's Cabinet of 20 ministers, six are women.
During Parliamentary question time this afternoon, the Green Party's women's affairs spokeswoman Jan Logie asked the Government why it was unable to find 10 women out of 1.8 million in New Zealand to be in its Cabinet.
Mr English, speaking on behalf of the Prime Minister, said: "I think there would be literally thousands who could carry out the functions of a Cabinet Minister.
"However, many of them choose to exercise those capacities in running their own businesses, in studying and looking after families and some of them fortunately enter politics and end up in the Cabinet of a National-led Government."
Mr English said it was up to National voters to decide the caucus' gender ratio, and that his party would not be committing to a quota for Cabinet or caucus.
"The Prime Minister, as I understand it, selects ministers on merit."
Earlier, the Green Party said they will also urge any coalition partners to have an 50/50 split of men and women ministers, though this would not be a bottom line.
"Half of the ministers in the next progressive government will be women and we will call on our coalition partners to do the same," co leader James Shaw told the Council of Trade Unions conference this morning.
Mr Shaw said government had to lead the way on equal representation.
"People will say it should be about the best person for the job, it should be about merit.
"In a perfect world, they're right. But in this world they're wrong."
Mr Shaw, a former business consultant, said one of the reasons many large companies struggled was because of a lack of diversity.
Businesses with women in governance positions traditionally did better, especially when it came to evaluating risk, he said. This finding could also be applied to governments.
National's Cabinet has a 70/30 ratio of male and female ministers. Only 32 per cent of MPs in Parliament are women.
Mr Shaw said this was not necessarily because of merit, but because Parliament was traditionally a male institution.
In a statement, he said: "The idea that people are paid on merit, or appointed to senior roles like Government Ministers based on their abilities doesn't stack up.
"Women are paid less largely because they're working in professions that are dominated by women, and they're often not appointed to senior positions because of barriers that have nothing to do with ability."
The Green Party's list is evenly split between men and women.
Women in Parliament
National: 16/59 MPs (27 per cent)
Cabinet: 6/20 (30 per cent)
Labour: 10/32 (31 per cent)
Greens: 7/14 (50 per cent)
New Zealand First: 3/12 (25 per cent)
Maori: 1/2 (50 per cent)
Act: 0/1 (0 per cent)
United Future: 0/1 (0 per cent)
Total: 37/121 (31 per cent)