A smoke billowing from a chimney is pictured, as the UN Climate Change Conference (COP26) takes place, in Glasgow, Scotland, Britain, November 6, 2021.
Just 32 of the 100 biggest private firms have set a target to reach net-zero carbon emissions, compared with 69 of the 100 largest public companies, the study showed.
In high-emitting sectors such as energy, infrastructure and manufacturing, only 14% of the private firms' annual combined revenue is covered by such a target compared with 77% of revenues from listed firms in the same sector.
“Private firms are falling devastatingly short on net zero compared with their publicly-listed cousins," said John Lang, project lead of the Net Zero Tracker.
As listed companies increasingly face mandatory climate-related disclosures, Thomas Hale, professor at Oxford University's Blavatnik School of Government, said there was a risk private firms escaped scrutiny and gained an unfair advantage.