New Zealand's largest-ever survey of gender representation across all levels of the workforce has revealed the extent of the imbalance at top of the corporate ladder.

The new Diversity Report, published by Champions for Change, surveyed more than 80,000 employees.

It found that males are over-represented in all levels of management from board level down.

At board level the composition was 64.6 per cent male and just 35.4 per cent female. In the key management personal category (which includes CEOs and COOs and similar roles) the split was 67 per cent to 33 per cent.

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The next category (other executives and general managers) was even worse at 69.5 per cent male and 30.5 per cent female.

The remaining two management categories (senior and other) had just 39 per cent and 45 per cent females respectively.

It was only when you got to the non-managerial category that the balance evened out - with 49 per cent male and 51 per cent female.

Champions for change co-chair Michelle Embling (chair of PWC) said she "unfortunately, wasn't surprised" by the results.

But she was heartened by scale of the study and the commitment to making a positive change that it represented.

"We want to move the dial here," she said. "This is step one and we want to see substantial change."

Measuring the starting point was crucial, she said. "It's like when you want to lose weight. When you step on the scales there's no hiding from it. The numbers don't lie."

What mattered from here was having the will at a leadership level because the change would come from the top, she said.

Champions for change is a group of 54 New Zealand CEOs and chairs from across the public and private sector who have committed to improving levels of diversity and inclusiveness in the business community.

The survey was run through 29 Champions for Change companies and polled 81,000 employees.

More organisations will participate next year once they have worked through the complexities of the assessment process, Embling said.

Champions for Change is convened and co-ordinated by the Global Women group.

Global Women CEO Miranda Burdon said the aim was to develop a question around ethnicity which could also return useful data for driving positive change.

Champions for Change co-chair David McLean (Westpac CEO) said the Diversity Report established "a baseline".

"It sizes the problem of under-representation of women in senior management roles, and shows that there is a particular drop off at executive and GM-level, flowing through to an under-representation in key management personnel and board roles," he said.

But what it didn't do was "show us exactly what we need to do to solve it", he said.

"In fact that is why the Champions group came together. If this problem was able to easily be solved we would have done it by now."