The parents of a boy who died from poisoning during river flooding are demanding an independent inquiry into their claim he was killed by a cyanide gas leak from a former landfill site.
A coroner has said Zane Gbangbola, of Chertsey, in Surrey, was killed in 2014 by carbon monoxide from a pump used to reduce flood levels at his house.
But Kye Gbangbola and Nicole Lawler dispute this, calling the conduct of the inquest unsatisfactory.
They promised to fight for "the truth".
But Spelthorne Borough Council, whose area includes Chertsey, said there was "no evidence" a leak of hydrogen cyanide from a former landfill site near the house had caused Zane's death, adding there was "no wider risk" to the public.
Shadow home secretary Andy Burnham has criticised the handling of the inquest into seven-year-old Zane's death, describing it as "seriously flawed".
In his parents' first interview since the verdict earlier this month, they told the BBC's Victoria Derbyshire programme they intended to campaign for a full public inquiry into their son's death in February 2014.
Ms Lawler said: "We were disappointed but not surprised [at the verdict], given the conduct of the inquest.
"We had profound concerns over the content and the conduct, the way that anything to do with hydrogen cyanide was marginalised, anything to do with carbon monoxide was magnified.
"We weren't given the witnesses that we called for. We'd called for significant disclosures that weren't there."
Mr Gbangbola, who was paralysed from the waist down in the same incident in which Zane died, said people did not "die from low-level carbon monoxide exposure", adding: "They're not routinely being carried by air ambulance to hospital in cardiac arrest."
Hydrogen cyanide - the chemical the couple allege had leaked from a landfill site - had been "clearly indentified" at their home next to the Thames, he said.
Mr Gbangbola said: "What happened here was the authorities were not investigated, simply exonerated."
He added: "The way in which you would get to the truth is by conducting full investigations into the areas that are of concern to us and the first responders. That wasn't done.
"In controversial cases, you do need to have independent people coming along to find out and look at all of the evidence in a proper, orderly manner, and that hasn't happened."
Recording his verdict at an inquest in Woking, coroner Richard Travers said the cause of death was "carbon monoxide toxicity from fumes generated by a petrol pump used by his family to clear the house of floodwater".
Zane was found unconscious by his mother and pronounced dead an hour later in hospital.
Zane's father Kye Gbangbola, who had been working upstairs in another bedroom, was left paralysed.
Spelthorne Council said it had been "a long and harrowing process for Zane's parents" and that "we continue to offer our condolences to the family".
Surrey Police have said no criminal charges will be brought over the boy's death.
The Victoria Derbyshire programme is broadcast on weekdays between 09:00 and 11:00 on BBC Two and the BBC News channel.