The panel said the mayor and London boroughs should expect major developments to incorporate living roofs and walls where feasible. It advised councils to reflect the policy in local development frameworks.
It also said the boroughs should encourage the use of "living roofs" in smaller schemes and extensions where opportunities arise.
Design for London (DfL) has led the work to develop the living roofs policy. Director Peter Bishop said: "We need to explore solutions to increase high-density living in the light of environmental considerations. Living roofs look to London's most underused asset, namely the space above our heads, to provide an answer."
Green roofs offer accessible extra space and together with green walls they can improve biodiversity and the appearance of buildings. They also help mitigate climate change by providing environmentally-friendly insulation and create sustainable urban drainage.
A technical report setting out the evidence for the London Plan examination, commissioned by DfL, will be published later this year. It outlines the benefits of living roofs, barriers to implementation and other countries in which they are used.
Subject to final approval from the government, the living roofs policy will form part of the revised London Plan, due to be published next March.