Now the owners of more than 3000 properties surrounding the former Pasminco lead and zinc smelter are about to be made "officially responsible" for the pollution they fought so hard to stop.

Proposed changes to Lake Macquarie City Council's Development Control Plan will make a blanket "assumption" that thousands of residential properties within a lead contamination grid, drawn up in 1995, are polluted by lead.

The highly-contentious grid is bounded by Boolaroo, Speers Point and Argenton and was used as a guide to determine where the highest levels of pollution from the smelter were.

It was originally established not to determine lead-contaminated properties, but to decide which children should be tested for elevated lead levels in blood.

Boolaroo Action Group spokesman Jim Sullivan described the changes as a way of making residents "officially responsible for pollution they had nothing to do with".

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Mr Sullivan said most residents were unaware of the proposed changes that "fly in the face" of the NSW government's polluter pays policy.

"This is about taking all the responsibility for the pollution away from council and the state government and placing it squarely on the shoulders of residents affected by the contamination," he said.

"Imagine the people of Williamtown being told in 10 or 15 years time that they are responsible for the pollution on their land. It's just not a fair outcome.

"I don't know how you say one person on the side of a grid line is contaminated and has to pay all this money and someone on the other side of the line isn't. How does the pollution stop at a line on a map drawn by people?"

Residential properties that are identified as containing black slag - a byproduct of the smelting process that was extensively used as landfill across the city for decades - will also be classified as contaminated.

Under the proposal, residents in the grid who submit a development application to council will be forced to follow a standard remedial action plan and pay to decontaminate their land. The cost is estimated to be up to $50,000.

Residents who can prove their land is under the Australian safety guideline for residential areas of 300 parts per million of lead in soil will be exempt.

Previously residents were required to test before getting work done to determine if their land was contaminated.

The proposed changes do not apply to commercial properties, schools, child-care facilities, public spaces or council-owned land.

The Cockle Creek smelter closed in 2003 leaving three suburbs with large swathes of land polluted by heavy metals to be cleaned up at residents' expense. Lead can cause brain damage and life-long health problems.

A council spokeswoman said the remedial action plan was designed to reduce costs for landowners.

She said the plan was a recommendation from the disbanded Lead Expert Working Group's report that was adopted by the NSW government in November 2017.

Lake Macquarie MP Greg Piper, who chaired the Lead Community Reference Group, said the proposal removed the need for residents to test their land for lead contamination before starting work.

Mr Piper said there was an "unfortunate history" in the area and residents were dealing with the "sins of the past", but this policy was about reducing the burden.

"If they are going to do something there will be an assumption that there is contamination," he said. "They don't have to go out and prove it one way or another... I don't think it makes life any worse, for most people it's an easier way ahead."

Boolaroo business owner and action group member Stan Kiaos said council was attempting to sell the plan as a win for the community, but the reality was the exact opposite.

"This plan could well be the final nail in the coffin for all residents in north Lake Macquarie after almost a decade of trying to realise a fair deal," he said.

"It has the potential for more and far reaching deterimental effects. It could be the forerunner to reversing the principle of polluter pays and putting responsibility for pollution on the residents."

The action group lobbied council to extend the consultation period for the proposed changes to allow for a public meeting.

Council's spokeswoman confirmed the consultation period had been extended to August 26 and said a council "pop-up stall" would be at Lake Macquarie Farmers' Market at Speers Point Park on July 27.

"The face-to-face session provides an opportunity for residents to ask about their specific property, allowing council staff to look up their contamination notation on the spot and advise them how the plan will apply to them," she said.

Boolaroo Action Group will hold a public meeting at Club Macquarie on Monday, July 15, from 6.30pm.