Up to 15,000 jobs could be created each year in London by 2025 as a result of Boris Johnson's plans to cut energy and tackle climate change, says a report.
The report, by Ernst & Young, bases its figures on the mayor's plans to make buildings more energy-efficient and building waste and recycling plants.
The report was commissioned by the London Development Agency.
But London Assembly Green Party Member, Jenny Jones, said commitment is needed from the mayor for the plans to happen.
The report also says £600m could be contributed to London's economy under the mayor's plans which also include introducing low carbon vehicles and the building of a decentralised energy network across London.
Mr Johnson said: "I see the green economy as an unprecedented opportunity not only to improve our planet and our quality of life, but to develop new industries and create new jobs in an economic climate that is otherwise extremely difficult."
But Ms Jones said the report will only go so far if it is not implemented.
"I think in the last year we have seen a huge number of really good environmental projects rolled back and we're actually losing momentum on the whole environment agenda," she said.
"We've got to see where the money is coming from to make these things happen and we've got to see some real commitment from the mayor which we haven't seen yet."