Key Points:

Public servants do just as much as those in the private sector but have greater job satisfaction and much bigger pay packets, a study has found.

The survey, published by Professor John Gibson of Waikato University in the New Zealand Journal of Employment Relations, showed the gap in pay between the public and private sector was between 17 and 21 per cent.

He said the study was based on 2005 data, "so given the faster rate of public sector pay rises recently, the premium is likely to be even higher now".

The research compared job information across both sectors and looked at variables such as stress, whether hard physical work was involved and the attitudes of workers to their employment.

It found many public sector workers - who were likely to be female, highly-educated and living in Wellington - had a "warm glow" feeling of contributing to society despite their jobs interfering with their lives at home.

Professor Gibson said the higher pay levels in government jobs had little to do with needing to compensate more to attract skilled workers, as the research compared like with like.

"So the fact that public sector workers actually get paid 20 per cent more is evidence of how out of line wage setting has been in the public sector," he said.

Professor Gibson said he believed public sector unions would push for big pay increases for their members before this year's general election.

"When public servants are based in swing electorates and it's coming up to an election year and they're seen as a pretty important constituency for one party or another, it's pretty easy [for the Government] to give in," he said.

But Public Service Association national secretary Brenda Pilott said the study had "no value".

"He calls public servants fat cats because a surgeon working at a public hospital earns more than a teenager working at McDonald's," she said.

"Of course the surgeon earns more because society places a higher value on saving lives than selling hamburgers."

Ms Pilott said the biggest pay increases in the state sector in recent years had been for doctors, nurses and teachers.

"Why? Because our society can't function without them and because we've struggled to hold on to them because they've been able to earn more overseas.

"I note that Professor Gibson is a public sector worker. Does he include himself in the fat-cat category?"

Figures from Statistics New Zealand showed the median salary and wage increase for the June 2008 quarter was virtually the same, at just over 4 per cent in both sectors.

In June, Finance Minister Michael Cullen said big pay rises for public servants were unrealistic.