The 200 largest firms operating in London's Square Mile can this week expect to receive a letter from the Corporation of London inviting them to sign up to a new City Climate Pledge scheme that would see them commit to disclosing their carbon footprint and climate change strategies.

Firms signing up to the pledge - which has been developed by the Corporation of London and environmental charity Pure, the Clean Planet Trust - would be obliged to annually measure and disclose the direct carbon footprint related to their energy use and employees' corporate travel and report on the measures they have undertaken to reduce their carbon footprint. They would also be offered the opportunity to offset their emissions using accredited offset providers.

Simon Mills, head of sustainability for the Corporation of London, said that the pledge would provide firms with a public stage from which to assert their commitment to reducing greenhouse gas emissions.

He added that many companies within the City were already undertaking emission reduction initiatives, but that the new pledge would provide an independent label backed by the Corporation of London.

"We live in a show-me, not a tell-me, world, and this pledge will help firms demonstrate what they are doing to limit the risk of climate change," he said. "We are expecting a great deal of interest in the pledge and Citrix and Bureau Happold have already signed up."

The scheme is expected to be self policing, but Mills insisted firms making the pledge would have to live up to their carbon disclosure and reduction commitments.

"They will be reporting figures that are transparent through company accounts," he said. "Any company exaggerating its actions would be easily detected and experience huge brand damage."

Mills added that there was a strong business case for City firms to sign up for such a scheme.

"With many financial institutions and insurance companies in the Square Mile, there is a real case for these companies to act to mitigate the risk of climate change," he explained. "They may not be as big emitters as manufacturing firms but with the datacentres in the city and employees' corporate travel, there is a lot that can be done to reduce emissions."