Businesses looking to secure government contracts will have to pledge to be net zero by 2050 under new requirements.
From September, firms seeking public sector contracts worth more than £5m a year will also have to publish “clear and credible carbon reduction plans” before being considered, the Cabinet Office said.
The move, which coincides with World Environment Day, is the first of its kind anywhere in the world.
It means that all firms bidding for contracts will have to meet the new criteria – not just those who win, a government spokesman said.
Under the new plans, a carbon reduction plan will have to set out where a company’s emissions come from and the environmental management measures it has in place.
COP26 will take place in Glasgow in November.
Speaking to Sky News, Lord Goldsmith, minister for the Pacific, international environment, climate and forests, said the UK is “blazing a trail” on climate initiatives, and other countries are following suit.
“I think the UK is doing more than any country than I’m aware of,” he said.
“We’re calling on the big multilateral development banks, like the World Bank, to make sure every decision takes into account the natural world.”
Lord Agnew of Oulton, minister for efficiency and transformation, said: “The government spends more than £290bn on procurement every year, so it’s important we use this purchasing power to help transform our economy to net zero.
“Requiring companies to report and commit to reducing their carbon emissions before bidding for public work is a key part of our world leading approach.
“These measures will help green our economy, while not overly burdening businesses, particularly small and medium-sized enterprises (SMEs).”