Wellington's Shelly Bay is an "accident waiting to happen" with at least one person already likely having been exposed to the risk of airborne asbestos without knowing it.

The site of a planned $500 million development has been occupied by a group called Mau Whenua for a year now. The group claims the Port Nicholson Block Settlement Trust went against the will of its own people when it sold its land for development and that the deal was done in secret.

Two notices have been recently issued telling the group to vacate the whenua. The second notice, issued by Wellington City Council, gave protesters 24 hours to leave the land by 6pm on November 17.

Council chief executive Barbara McKerrow made the decision citing health and safety concerns regarding imminent construction on the developer's adjoining land and asbestos risk on council land. The protesters are yet to move but are in de-escalation talks with the council.

She made the call after receiving information including a soil sample report from Fibresafe.

Wellington City Council chief executive Barbara McKerrow. Photo / Mark Mitchell

A follow up email from Fibresafe regarding that report said the council needed to consider the level of control it had over the site and buildings.

"For example, I have observed that the current site occupants appear to have broken into, and are living in, the guard hut at the southern boundary of the site", the author of the email, whose name has been redacted, said.

The author recently helped oversee a repair of a broken window in Shed 8 and noted it appeared someone had broken in and accessed the building.

If that was the case, whoever it was would have been in close proximity to both damaged and degraded asbestos fibre cement and to damaged asbestos insulation, the email said.

"This person or persons have now been exposed to the risk of airborne asbestos fibre without knowing it.

"I recognise the sensitivity of issues at the site, and while I sympathise with what the group currently occupying the site is trying to achieve, putting aside politics, the whole site is an accident waiting to happen."

Protestors and Māori Wardens have set up check points on the road in and out of Shelly Bay. Photo / Mark Mitchell

The email said allowing the site's occupants to remain "anywhere near" the buildings in their current state would continue to present an ongoing risk.

Mau Whenua spokesman Wayne Makarini said to the best of his knowledge, no one from the land occupation has broken into any buildings.

"The buildings have been left for all manner of members of the public to go through over many years and I believe there have been a number of incidents of vagrants going through.

"We can't be held accountable or responsible for the general public's use of public land."

Makarini stressed they were occupying the land- not the buildings, and he was confident everyone who was a part of the occupation was safe.

Wellington City Council spokesman Richard Maclean confirmed the land was closed it was not lawful for people to remain there.

"Council officers have been working with Mau Whenua on a peaceful resolution for several months as new information has come to light regarding asbestos related hazards as well as impending construction activity. We are not in a position to provide more detail at this time."

An artist's impression of an aerial view of the proposed development of Shelly Bay. Image / Supplied

MacLean said those occupying the land needed to vacate as soon as possible for their own health and safety and that of anyone else who might enter the site.

Mau Whenua have been fully informed of the risks of remaining on site, MacLean said.

According to the Ministry of Health intact asbestos-containing material is not a risk merely by its presence. Potential health problems occur if asbestos fibres become airborne.

The health effects of exposure can take many years, sometimes up to 50, to develop and people are more likely to experience effects when they are exposed to higher concentrations of asbestos, are exposed frequently, and over long periods of time.

Resulting diseases and conditions include asbestosis, pleural plaques, lung cancer, and mesothelioma.