Wellington nurses Erin Kennedy and Ann Simmons strongly believe in equal pay for work of equal value.

As political apparatchiks' salaries soar to record highs, female workers are set to file a major equal pay case in the High Court.

They will allege hundreds of women are being significantly underpaid.

The move follows a ground-breaking Court of Appeal decision last year that female-dominated industries should receive a rate of pay equal to what would be offered if that group were male-dominated.

The decision was made after legal action taken by aged-care worker Kristine Bartlett against her employer TerraNova Homes and Care, for equal pay.

Experts said the precedent would open the floodgates to a range of related cases. Over 2500 claims were filed last year with the Employment Relations Authority by aged-care workers claiming low pay based on gender discrimination similar to Bartlett.

Nursing was one profession expected to follow Bartlett's suit as the long legal battle concluded.

The new pay equity suit comes as figures reveal a third of staff working at the Beehive now earn six-figure salaries.

Despite the restraint promised by National when they came to Government, Ministerial Services employees have continued to pocket healthy pay rises each year.

The average salary of staff working in the offices of ministers hit $93,298, an increase of more than 5 per cent over 2014, official figures show. The average salary for a New Zealand nurse, with three to five years' experience, is between $54,000 and $64,000.

Of the 155 officials, 53 earn in excess of $100,000 a year and 23 earn more than $130,000.

Several senior officials, notably John Key's long time chief of staff Wayne Eagleson, are thought to earn more than a basic MP's salary of $150,000, although official figures do not disclose names.

Wellington nurse Erin Kennedy said the time had come to address society's underlying undervaluing of traditionally female jobs. She has worked as a surgical nurse for 10 years.

Some of the pay, work hours and conditions offered to her and her colleagues was "a slap in the face", Kennedy said.

"Nursing and caregiving is hard physical work. There's an awful lot of nurses with replacement hips and knees and back issue ...

Our nurses do a great job, and they should be recognised for it."

Her colleague Ann Simmons said it was unforgivable that mental healthcare employees, many on the minimum wage, often could not make ends meet, especially considering assault was a common work risk.

"There are some weeks where people can't pay the rent and their children can't go to school functions. They're not earning enough to do the things that we take for granted."

New Zealand passed its Equal Pay Act in 1972, and though women have made significant gains in the four decades since, experts are warning progress has faltered in recent years.

In general, the gender pay gap has been decreasing in the last two decades, but last year it grew 7 per cent , according to Statistics New Zealand's Quarterly Employment Survey. In 2014, men earned roughly 10 per cent more than women for an hour's work.

Overseas, the "nurses vs firemen" debate saw Birmingham City Council in the United Kingdom faced with payments estimated at $1.8 billion to settle equal pay claims after cooks and cleaning staff discovered they were denied bonuses offered to rubbish collectors and street cleaners.