The Environment Minister has called for New Zealand to improve its fresh water management following a report finding almost a third of the country's lakes have poor water quality.

The Status and Trends 2010 Report on Lake Water Quality in New Zealand, released yesterday, presented the findings of water quality tests on 112 lakes between 2005 and 2009.

Sixty-eight lakes had reliable data for the period 2005 to 2009 to enable trends in water quality to be measured. Nineteen lakes showed deterioration and eight showed improvement.

"This report concludes that New Zealand lake water quality compares favourably with Europe and North America but there are signs of real concern," Environment Minister Dr Smith said.

"It is unacceptable that 32 percent of our monitored lakes have poor water quality and that more lakes are deteriorating in water quality than are improving.

Mr Smith said lake water quality is worst in low-land intensively farmed areas such as the Waikato and Manawatu.

"The Government is ramping up spending on freshwater clean-up initiatives, from $17 million from 2003-2008 to $94 million from 2009-2014. It is encouraging the lake showing the greatest improvement in water quality is Lake Rotoiti in the Bay of Plenty, proving the success of the Rotorua Lakes Water Quality initiative."

Lakes in the Canterbury region made up 15 of the 19 lakes where water quality had deteriorated between 2005 and 2009.

"This reinforces the Government's decision to intervene in water management in Canterbury, and the need to fast-track water plans and rules to better manage pollution.

Dr Smith said the report will contribute to the Government's programme of improving water management.

"The data in this report is not comprehensive and has some gaps. More information is required on why the greatest deterioration in water quality has occurred in catchments with more native than pastoral land cover. The data is also limited to 112 out of 4000 New Zealand lakes, although I am encouraged that the number of lakes being monitored has trebled since 2000.

"I encourage New Zealanders to participate in the Land and Water Forum consultation between now and March on the steps we need to take to improve freshwater quality."

The Green Party's co-leader Dr Russel Norman said the report demonstrated why the country needs clean water rules to protect waterways.

"Almost a third of all lakes in New Zealand are unhealthy, and many are getting worse," he said.

"New Zealanders love our rivers and lakes, and we want to protect them. Our kids have a birthright to swim and fish in our waterways, but this legacy is at risk."

Dr Norman was sceptical of the reasons why the release of the report was delayed. It was to be released last week.

"It is interesting timing that the report's release was delayed during the World Dairy Summit in Auckland, when the report concludes that pastoral land use is associated with the ecological deterioration of our lakes."