LONDON – Staff at an influential corporate climate action group whose board announced a plan to allow companies to offset greenhouse gas emissions from their supply chain with carbon credits has now found such offsets are largely ineffective, a confidential preliminary draft shows. At stake is the growth of the still nascent market for voluntary carbon offsets. …The Science-based Targets initiative (SBTi), a U.N.-backed nonprofit that audits the emission reduction plans of companies, triggered a revolt among staff last month by declaring its intention to allow use of carbon credits prior to concluding its research. Since then, the SBTi’s board of trustees said that any decisions would be “informed by the evidence”. …Many of the SBTi’s financial backers are pushing for adoption. They argue offsets are needed to spur more investment in clean energy and meet a global pledge to reduce emissions to zero on a net basis by 2050.