Westpac will join Genesis Energy in the don't ask approach.
McLean, who chairs the Champions for Change - a group of private and public sector chairs and executives who are trying to shift the dial on diversity, said it was often hard to work out why there was a gap in pay or lack of women in board and executive ranks without drilling below the surface.
"Most are not conscious decisions or malicious but are just the way the system works."
McLean has also made changes to the bank's recruitment process forcing both its internal recruitment team and external recruiters to put forward at least two female candidates for every position.
"I made it a rule that I was not going to sign off any hires until they had a short list with at least two women on it."
He said that forced the recruiters to go look for candidates in a different way.
The state sector has just broken through a new record in the number of women that sit on its boards.
Julie Anne Genter, Minister for Women revealed Thursday night, that women made up 47.4 per cent of directors in the state sector in 2018 - up from 45.7 per cent in 2017 - and another step closer to the Government's target of 50 per cent by 2021.
Genter said the Government was committed to having more women in leadership roles and hoped to inspire the private sector to lift its game.
"We're encouraging organisations across New Zealand to challenge current workplace cultures and support women into leadership roles, not just because that's the fair thing to do, but also because diversity helps organisations function more effectively."
McLean said the Government's achievement would put pressure on the private sector.
"It is healthy pressure - what the government has shown is that you can do it."
The public sector is well ahead of the private sector. Latest figures for the NZX show just 22 per cent of directors were women in 2018.
While research released by the Champions for Change in October found its members had just over 35 per cent women on boards.
McLean said the 54 organisations involved were up for the challenge and had committed to finding balance.
Instead of aiming for 50-50 men and women it has a target of 40-40-20. That is 40 per cent men, 40 per cent women and 20 per cent which could be either.
It also doesn't have a deadline for achieving that.
McLean said its focus was more on measuring the data and making progress.
"The best thing we can do as a private sector organisation is publish the data and hold ourselves to account."
At Westpac New Zealand three out of its eight directors are women including chair Jan Dawson and four out of nine of its top executives are women.
McLean said across its leadership team more than half (51 per cent) were women and that had risen from the low 30s.
Critics worry that women will be appointed to roles based on gender alone rather than merit in order to meet targets.
McLean said that was a challenge and he also had women saying to him that they wanted to be appointed on their merit not on a gender basis.
"I say that is fine, but in my whole professional career it has always been appointment based on merit and yet the gender balance hasn't shifted.
"So therefore either women have less merit - which I don't believe - or there are other things going on."
McLean pointed to institutional bias as being a cause and said sometimes it was because people wanted to replace someone who leaves with a similar person and that meant they had a male in mind.
The other challenge was that what men and women valued could differ in the workplace.
An example of that was having the flexibility to allow people to pick up their children from school or a career break to start a family.
He said adjusting the way people worked was important in breaking through those cognitive biases.
