Fear of multi-billion-euro lawsuits from fossil fuel investors is putting the Paris agreement on climate change at risk, one of the deal's architects has warned. Compensation claims from a pact that allows companies to sue countries over policies that affect their investments could amount to more than a trillion euros by 2050, according to one estimate. The Energy Charter Treaty (ECT) was originally drawn up to protect energy firms as the Soviet Union crumbled, but new analysis suggests it could allow coal plants in 54 signatory states to keep belching carbon dioxide for more than a decade. "The integrity of the Paris agreement is critically undermined by the Energy Charter Treaty," said Laurence Tubiana, the French climate change ambassador during negotiations for the Paris agreement. "Europe and others should withdraw from this shambolic and dangerous anachronism if we are to stay within 1.5C (of global warming)," she told the Thomson Reuters Foundation. The treaty's primary aim was to protect investments by European Union energy majors in Russia and the new republics said Yamina Saheb, the ECT's former energy efficiency chief, who left in June 2019. "What they never thought about is that the treaty could be used against the EU countries themselves," added Saheb who is now working as the lead author of a U.N. Intergovernmental Panel on Climate Change working group on climate mitigation.