A campaign group has questioned whether Olympic chiefs followed “due democratic process”, after they admitted transporting construction waste to Leyton Marsh before a planning meeting which decided whether they were allowed to use it.

The Olympic Delivery Authority (ODA) outlined its proposals in a 114-page plan to use heavy-duty construction waste as the subsoil layer for the site where a temporary basketball training venue had been built on Metropolitan Open Land, behind Lea Bridge Road ice rink.

Many local people wanted the ODA to use soil which would support biodiversity used, rather than construction waste which they say would be more suited for use under a road or large permanent structure.

More than 1,000 people signed a petition calling for cleaner soil and wanted the matter debated at Waltham Forest Council’s planning meeting on September 12.

However the day before the meeting trucks brought several mounds of construction waste to the site.

“Fill was brought to site by our contractors in anticipation of a positive decision, allowing them to commence work in a timely fashion given the tight timescales for handing the land back to the Lee Valley Regional Park Authority on October 15,” said an ODA spokesman.

“We can confirm that no fill was used ahead of the planning committee meeting.”

Caroline Day from the Save Leyton Marsh (SLM) group which was set up in January to oppose the application for the temporary venue, was outraged.

“It’s one of most crucial aspects of reinstatement,” she said.

“SLM group would like to know why the ODA were in ‘anticipation of a positive decision’ at the council meeting.

“Even if the planning officers recommended approval, this recommendation does not equal a guaranteed decision on behalf of the councillors, and provides no justification for delivering materials for a particular reinstatement plan that had not yet acquired permission by the planning committee,” she said.

“This matter has very serious implications for due democratic process and needs to be investigated further.

“Are the council and the ODA consulting so closely that the ODA are aware of what decisions are likely to be made?” she asked.

A spokesman for Waltham Forest said: “The criticism is they put the soil there before the decision was made, but the decision vindicated what they did in as much as the soil was ok, so in our perspective I don’t see a problem, they met the requirements.

“At that meeting we made the decision the soil the ODA procured was appropriate.

“They have looked at what would be the correct type of soil and they were correct in that anticipation because that was the decision of the planning committee.”

Many Hackney residents who use Porter’s Fields for recreation were up in arms when Waltham Forest councillors awarded the MOL site planning permission.

Their anger deepened when it emerged asbestos – which is dangerous to human health when airborne – had been dug up and the piles of rubble containing it were left on site uncovered for weeks.