Green500 provides advice on matters such as reducing carbon emissions, improving energy efficiency, water usage, waste management and transport plans.
Members can work with a specially designated carbon mentor and expert, who will help develop a tailored emissions reduction plan.
Crowne Plaza - The City, part of InterContinental Hotels Group, has already put a number of sustainable practices in places, including a green private car hire service, an in-house tidy team award and water saving devices in all bedrooms.
Paul Brackley, general manager, said: "We are fully committed and aligned with the Green500 strategy and are always looking for new innovative ways to reduce, reuse and recycle as part of our ongoing environmental journey."
Other companies to have signed up include Chelsea Football Club, EDF Energy, Marks & Spencer, The John Lewis Partnership, Eversheds, T-Mobile, Guy's and St Thomas' Hospital, Ernst & Young and Kings College London.
By Daniel Thomas
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