US oil giant Chevron has launched a legal appeal against a $9.5bn (£5.9bn) fine by an Ecuador court for polluting much of the country's Amazon region.
Chevron accused lawyers and supporters of the indigenous groups who brought the case of "corrupting" the trial.
It said the judgement contained "numerous legal and factual defects".
The oil firm Texaco, which merged with Chevron in 2001, was accused of dumping billions of gallons of toxic materials into unlined pits and rivers.
Protesters said the company had destroyed their livelihood. Crops were damaged, farm animals killed and cancer increased among the local population, they said.
An appeal by Chevron had been widely expected. A statement by Chevron said the firm would pursue efforts at an international tribunal and in the US courts to prevent the ruling from being enforced.
No payment can be made during the appeals process, which could drag on for years.
The appeal is the latest twist in the case, which was brought on behalf of 30,000 Ecuadoreans nearly two decades ago.
Ecuadorean Indian groups said Texaco dumped more than 18 billion gallons (68 billion litres) of toxic materials into the unlined pits and rivers between 1972 and 1992.
The plaintiffs said the company's activities had destroyed large areas of rainforest and also led to an increased risk of cancer among the local population.
The trial began in 2003 after almost a decade of legal battles in the US. At that time, a US appeals court ruled that the case should be heard in Ecuador.
Environmentalists hope the case will set a precedent, forcing companies operating in developing countries to comply with the same anti-pollution standards as in the industrialised world.