New Zealand has been ranked near the top of an international report judging how well it treats the growing number of people over-65 who are still working.

A report by the financial company PricewaterhouseCoopers (PwC) shows nearly 40 percent of New Zealanders are working until they are 70 and that number is rising.

Its report, ranking 34 OECD countries, puts New Zealand in second place in how it treats older workers, only behind Iceland.

In its own words, the country is "harnessing the economic power" of older workers.

As well as more over-65's working, PwC said New Zealand had a great record for allowing them flexible conditions, and a relatively low gender pay gap.

It was also about their skills being better appreciated, said a partner for the company, Scott Mitchell.

"They are as useful, if not more, especially when they can be in a flexible working environment," he said.

"Just because you become an aged worker, the mere fact you've got someone who's been there and done that and has maturity - they can be fantastic coaches."

The government's statistics show of all over-65's, one in five is working - that is expected to rise to one in three in 20 year's time.

There are several reasons why older people keep working, said a co-director of the Retirement Policy and Research Centre at Auckland University, Susan St John.

"Among them of course is the problem of outliving savings and needing to provide extra because there's a greater awareness that New Zealand's Super scheme, while generous, isn't enough for many people," she said.

People should be judged on what they are able to do, rather than a ticking clock, said former All Blacks doctor and current chief medical officer for Sovereign, John Mayhew.

"There's no evidence that work is bad for us, it may be better in fact. As long as someone is physically and mentally able to do the job they want to do and they enjoy it then carry on," he said.

"For most of us there's no magical cut-off at 65, I think we should push the retirement age up."

PwC's report also calls for the government to look at the retirement age, but Ms St John said just because more older people are working, it did not mean it should go up.

"That is a real can of worms because many people are not capable of staying in the workforce and raising the age puts them on a work benefit, for example," she said.

The government has consistently batted away calls to lift the age, saying 65 is affordable.

MsnSt John said it was worth noting statistics do not take into account older people who spend much of their time in unpaid caregiving roles - that could mean simply looking after grandchildren.