Contamination of land at the Waterside Drive development will be further investigated later this year, as a councillor warned against complacency.

Hotspots of contamination caused the application, which has outline planning permission, to stall in July last year and the council investigated at a cost of about £700,000.

But the issue remains, and there were concerns the application would be pushed through regardless, or fail completely.

Teresa De Santis, who owns the Weir pub, near the site, noticed a “potential hotspot of contamination” near buildings on the site associated with Walton Casuals Football Club. The Little Tots Nursery uses space in one of these buildings.

She met Elmbridge Council last month to discuss health issues resulting from airborne, ground and ground-water toxins, and asked if the nursery had been informed.

She was told it was the responsibility of the football club to do so, so she wrote to the nursery and parents herself.

Councillor Chris Sadler said the nursery should have been made aware of the contamination and potential risks and was baffled as to why a proper risk and cost assessment was not done before plans were made, because the council had been involved in projects at Waterside Drive in the past and encountered similar problems.

Discussing the death of seven-year-old Zane Gbangbola in nearby Chertsey in 2014, from what his parents believe was poisoning was from contaminated water from a landfill site, Coun Sadler said: “The whole area of land contamination is a very technical one and I think it’s one that our experiences are growing in. It’s arguable that we have been overly complacent about it in the past.”

Ms De Santis said: “The main risk to human health in this report are via volatile aliphatic and aromatic hydrocarbons [gas] fractions. Which means you breathe them rather than see them and some do not have an odour.”

She apologised for potentially shocking parents but believed they “should have been made aware of the circumstances of having vulnerable toddlers in the potentially dangerous environment and to the parents especially”. She said when she spoke to parents some had no idea of the contamination.

Judith McFarlane, technical administrator at Cognition Land and Water, based in Weybridge, said: “With these kinds of sites, they have to take preventative methods and have to reach certain thresholds. They have to exceed that standard in order to go ahead with the development.”

To deal with the leeching of gas, Ms McFarlane said a membrane was fitted that would “stop it [the gas] travelling into the ground water” adding: “Obviously everyone’s always worried when there’s children involved.”

David Ions, UKIP candidate for Walton North, said: “I am concerned about the extent of contamination found in Waterside Drive, the spiralling costs and the lack of transparency regarding the true cost of the sports hub.”

A council spokesman said the investigations did not show any health risk and said: “The council has informed Walton Casuals FC of the results of the contamination survey and, in particular, the results relating to their ground, as the existing lease is with the football club.

"Following very detailed investigations we are not aware of any immediate health concerns to users of, or visitors to, the site.

“The council will continue to monitor the position and the intention is to carry out further investigations later this year either as a part of the sports hub construction or separately if the hub is not agreed.”

The development would rehome Walton Athletic Club and Walton Casuals FC with Walton and Hersham moving from Stompond Lane.

This newspaper contacted Little Tots Nursery and Walton Casuals but neither were available for comment.