GNS Science chief executive Mike McWilliams was the highest paid CRI boss in the last financial year.

A 75 per cent increase in the boss's salary at Crown-owned company GNS Science has prompted speculation of a golden handshake.

Mike McWilliams was chief executive of the research institute until May 2016, when he resigned.

But according to GNS Science's annual report, the chief executive's pay packet jumped from the $450,000-$460,000 band in 2015 to $790,000-$800,000 in 2016.

GNS SCIENCE Crown-owned company GNS Science manages natural hazards and carries out scientific research across the country.

This puts the chief executive's salary at least 25 per cent higher than any other Crown Research Institute boss.

READ MORE:

* Revealed: The highest paid public servants

* State Services Commission reveals gender pay gap in public sector

* NZ judge could become Britain's top paid public servant

* Calls for state broadcaster to reveal pay packets

The closest is AgResearch chief executive Dr Tom Richardson, who is paid up to $670,000.

GNS Science was asked whether McWilliams, who had been at the helm since September 2013, received a payment to leave, and was asked to explain the salary jump. It declined to comment.

It would also not reveal the salary bracket for incoming chief executive Ian Simpson, who is due to start in January. Simpson is the former boss of the Earthquake Commission.

Science and Innovation Minister Steven Joyce has been asked to provide an explanation on the increase, and whether he was made aware of it.

LABOUR: PLEASE EXPLAIN

Labour finance spokesman Grant Robertson said the Government should explain why such an "extraordinary sum of money" changed hands.

"It does appear as if it relates to some kind of payout, as oppose to a straight salary increase.

"Whatever the situation, GNS and the Government need to explain what is either a massive pay increase or a golden handshake.

"This seems like an extraordinary sum of money. Taxpayers will be wondering what on earth is going on in this organisation."

Green Party co-leader James Shaw said he could not comment on the specific case, but said pay increases of public sector bosses was a concern.

"Public sector chief executive salaries have been rising fairly steeply, when the vast majority of the public or private sector are not."

WHAT IS GNS SCIENCE?

GNS Science is a Crown-owned company that employs 372 science and support staff and has offices in Lower Hutt, Taupo, and Dunedin. It also owns and manages earthquake monitoring centre GeoNet.

Its purpose is to carry out research that increases resilience to natural hazards and drive innovation and economic growth in the energy and minerals industries.

In 2016, the bulk of its funding came directly from the Crown (33.1 per cent), and 25 per cent came from contestable funding pools, primarily from the Ministry of Business, Innovation and Employment.

The rest was from GeoNet and commercial investments, both in New Zealand and overseas.

CRI BOSSES: WHAT ARE THEY PAID?

AgResearch: $660,000-$670,000

ESR: $400,000-$410,000

Landcare Research: $440,000-$450,000

Niwa: $620,000-$630,000

Plant and Food Research: $580,000-$590,000

Scion: $450,000-$460,000

Callaghan Institute: $570,000-$580,000

GNS Science: $790,000-$800,000

Source: Individual CRI annual reports for the financial year ending 2016