The PA firm helped Cameron to persuade BSkyB CEO James Murdoch and Tesco chief executive Sir Terry Leahy to share a platform with him at the event.
Media Strategy also pulled in 200 senior figures from the City, as well as ‘green entrepreneurs' and think-tanks.
The event, marking a rapprochement between the Tory leader and employers, was hailed as a coup for Cameron.
It threatened to overshadow a speech on the environment by Gordon Brown scheduled for the same day.
Murdoch and Leahy outlined what is required for the economy to grow in a way that protects and enhances the environment. Leahy said going green will increasingly be ‘good business'.
Media Strategy MD Charles Lewington chaired a debate on how green entrepreneurs can gain access to the capital necessary to fund their ideas.