New Zealand's under-employment figures are hiding a complex situation.

One in five part-time workers - or 112,000 people - want to work more hours.

But EY employment lawyer, Christie Hall, says there are probably good reasons those people can't get the work they want.

She told Mike Hosking that could include their location, work industry, or their responsibilities such as children.

"It may be not what they want but it is their situation in life at that point of time, so I think those sort of factors do play into the statistics.