The council still wants to go ahead with plans to build a cricket pavilion on Hackney Marshes – despite a report saying soil there has dangerous contaminants over acceptable levels.

The presence of chemicals on the site – including heavy metals, asbestos fibre, acid and alkali sulphates – came to light after a Freedom of Information (FoI) request submitted by campaign group Save Lea Marshes (SLM).

SLM members fear a repeat of the 2012 Leyton Marsh scenario when Olympic chiefs were accused of allowing piles of rubble contaminated with asbestos to be left uncovered for weeks while building a temporary basketball court on protected metropolitan open land.

Once dug up there is a risk the chemical fibres become airborne, putting people at risk of breathing in the carcinogenic fibres.

Six unexploded Second World War bombs are known to have landed on Hackney Marshes which remain undetonated and bomb rubble is known to be buried on the earmarked site.

SLM spokesman, Caroline Day, said the list of contaminants is “significant by any reckoning”.

She said: “It is clearer than ever that an unjustifiable risk to local people, animals, as well as the secondary aquifier and local flora and fauna, is posed in digging up previously undisturbed ground.”

SLM members are calling on the council to build the cricket pavilion on the footprint of the present outdated North Marsh building rather than a new design which includes a 68-space car park on the open green space.

The group found documents about a design given planning permission by the government’s Planning Inspectorate in 2009.

At the time the council claimed this was the “optimum location” for the pavilion to ensure it did “not impact on the open nature of the Marshes”.

But this year the council claimed construction of the 2009 design was impossible, because of a water main running through the site.

However documents show the water main runs alongside the river and would have no effect on the consented plan.

After repeated queries from the Gazette, the council admitted the 2009 plan is only impossible because it wants to include a car park in the plans.

A council spokesman said: “Although the soil investigation report for North Marsh does identify some contamination, the levels discovered are not exceptional for London. The construction process involves identifying the contaminants present and identifying remedial measures to mitigate against any adverse effects on construction workers and the public.”