A council has unanimously backed the family of a seven-year-old boy who died during floods in Chertsey in 2014 and agreed to call for a full inquiry.
Spelthorne council has passed a motion that "crucial" evidence over Zane Gbangbola's death was ignored.
Zane's parents claim he was killed by hydrogen cyanide gas washed out of an old landfill site behind their home.
An inquest ruled he died from carbon monoxide from a petrol-powered pump used to clear floodwater in the house.
The couple have always insisted the pump was not in use.
'Expose the truth'
Mr Beardsmore told the meeting Spelthorne was 20% under water, with many people living near waste sites and disused gravel pits, adding: "It could have been any of us."
He produced a report showing high levels of hydrogen cyanide were recorded on the day Zane died and a government Cobra meeting was held, but said: "This report was not accepted by the coroner and more importantly, five more pages of this report were 100% redacted."
He also produced a medical report for Zane's father, Kye Gbangbola, who was paralysed in the incident, and said a consultant attributed his condition to hydrogen cyanide.
"We know Porton Down were called in," Mr Beardsmore said. "The coroner did not even call their evidence."
Councillor Chris Bateson, a Liberal Democrat, listed high-profile cases including the Stephen Lawrence inquiry and Hillsborough, saying: "The powers-that-be don't always get things right."
Labour councillor Veena Siva said Zane had been denied an inquest with a jury when there was "a litany of evidence on the toxic nature of the landfill site".
The motion was also supported by the Conservatives, the United Spelthorne Group and the Green Party.
Coroner Richard Travers, an independent member of the judiciary, has never commented on the case.
After the meeting, Zane's parents said: "We emphasis we will never win, Zane will never win, he has been taken from us, but we can expose the truth and protect others.
"It has been almost seven years on since Zane's passing and he was only seven years old when he died. This has simply taken too long."
Under the motion, all parties on the council will sign a letter to the home secretary calling for an immediate independent panel inquiry.