Wellington, June 10 NZPA - The discovery of chemicals in a New Plymouth children's playground has led the Green Party to call for a national register of contaminated sites.

Two drums containing chemicals were found by workers laying a stormwater drain in May at Marfell Park, the site of the city's former dump.

After further excavation, at least seven other drums were found.

The chemicals -- tetrachlorobenzene and trichlorophenol, both used in the manufacture of herbicides -- were said not to be a public health risk, though such chemicals can generate dioxin.

People need to know where such contaminated sites were, Green Party spokeswoman Catherine Delahunty said.

"In the interest of public safety we must take these risks very seriously and act with precaution.

"We have no national list of contaminated sites. This means that the clean-up funds are not necessarily being spent on the most dangerous sites."

A "methodical and rigorous programme" of soil sampling and historical investigation was needed, Ms Delahunty said.

A national register would allow for proper identification and isolation of contaminated sites, she said.

"We simply do not know how safe many sites are and, until we do, we must treat them as a potential risk to the public."

The New Plymouth District Council launched an investigation in 2001 after fears that a cancer-causing dioxin waste from the Ivon Watkins Dow agri-chemical plant in the New Plymouth suburb of Paritutu was buried at sites around the city.