The NSW government "suppressed" evidence that soil underneath Allianz Stadium was potentially contaminated with carcinogens during a botched planning process to knock down and rebuild the facility, a Sydney court has been told.

Community group Local Democracy Matters on Wednesday laid out its case against the state government in the Land and Environment Court in a bid to prevent the stadium’s demolition before the March state election.

The NSW government plans to knock down and rebuild Allianz Stadium in Moore Park at a cost of $730 million in addition to the refurbishment of Olympic Park’s ANZ Stadium.

In his opening statement, lawyer Tim Robertson said Infrastructure NSW had information on groundwater and soil analysis tests which had revealed traces of carcinogens in the soil beneath the city stadium.

The information on the contamination was not included in the Environmental Impact Statement, Mr Robertson told the court.

He added the levels of contamination were “well in excess of the criteria for recreational use”.

LDM also argues the government didn’t exhibit the stadium demolition proposal for the required period of time and failed to consider design excellence.

The community group’s case is being heard concurrently with an action brought by Waverley Council, which is also challenging the knockdown.

Both NSW Labor and the Greens oppose the government’s controversial $2 billion stadiums plan which includes upgrading ANZ Stadium at Olympic Park and a new facility at Parramatta.