Three seemingly smooth and well-tended parks could slip and leak poison into waterways unless they get a multimillion-dollar clean-up.

Auckland City councillors vote today on a proposal to spend $11 million over the next 10 years resealing old landfills under Newmarket Park, Waikowhai Park and Meola Reef. If they vote yes, the public will have a chance to comment before the spending gets final approval in mid-year.

Marcus Herrmann , acting manager of recycling and waste operations. said slips were inevitable at sloping Newmarket Park - which is topped by a playground - unless the old landfill beneath it was properly sealed. The park, which had major slips in 1979 and 1996, rests on one of 45 known or suspected council-owned closed landfills in the city.

Two other landfills that have become popular parks - Waikowhai Park on the Manukau Harbour and Meola Reef between Pt Chevalier and Westmere - are oozing or threaten to ooze toxic fluid from rubbish dumped when they were tips.

Councillor Aaron Bhatnagar said the landfills were never sealed properly when they were closed in the 1960s and 1980s. They were the last three needing major work.

At Newmarket, old tyres, batteries and hunks of rusted metal have come up from the ground and dot the tree-covered slope beneath the playground.

Mr Bhatnagar said the old rubbish had encouraged new, illegal dumping, and the combined mess was leaking smelly metal residues into the stream at the bottom of the slope and out into Hobson Bay.

"Put it this way, you wouldn't want to eat it and you wouldn't want to touch it."

Newmarket Park - in Mr Bhatnagar's Hobson Ward - is first on the list to be resealed. Capping the landfill and re-grading the slope would cost $5 million over three years and could start at the end of this year.

Waikowhai Park would be next, costing $4 million to reseal over three years from 2013 to stop it leaking to the Manukau Harbour.

A new seawall to stop erosion at the edge of Meola Reef would cost $2 million over two years, starting in 2016.