ASSEMBLY chiefs are urging Newport planners to think carefully before building a school on a former landfill site contaminated with potentially lethal poisons.

The city council wants to build the replacement for Durham Road schools on the Glebelands former landfill site.

But indpendent testing carried out on the site - where Newport council also wants to site hundreds of homes - shows the land is contaminated with cancer-causing chemicals, including arsenic and mercury.

The replacement school and new homes would be built under the Private Finance Initiative by Vinci, the PFI contractor, in partnership with the council, which commissioned consultants White Young Green Environmental to test the soil with boreholes.

The findings are in a report submitted to Newport council for consideration before planners discuss granting full planning permission.

The scheme already has outline permission, and the council says the contaminants problem can be overcome by putting a concrete cap on the site.

A copy was also sent to the National Assembly - which is now warning the city council to carefully consider its decision.

An Assembly spokeswoman said: "The Assembly administration has asked the council to ensure that it considers the matter fully before taking a decision to grant full planning permission. The council has commissioned further work, and they now need to consider the report and its implications before deciding how to proceed on the planning application."

The report states: "Arsenic, benzene, lead, mercury, nickel are present and represent a potential risk."

All of the chemicals are designated C7, which means they are carcinogenic.

A spokeswoman for Newport council said: "The council would not have gone ahead if it had not been assured by experts that the site can be made safe by capping it with concrete.

"Safety will be assessed by the Environment Agency, who will provide an independent analysis ensuring complete safety.

"The advice the council has received is that once the remediation works have been carried out the site will meet government safety standard and will be a safe site. The council won't go ahead without that guarantee."