More than 120 leading elected members and senior officers from Barking and Dagenham, Enfield, Greenwich, Havering, Hackney, Newham, Redbridge, Tower Hamlets and Waltham Forest attended a conference.
The Local London: Driving Growth through Devolution event took place in Stratford, Newham in east London.
A prospectus for devolution is due to be published next month, following on from discussions which took place. It will detail the shared vision and ambitions of the boroughs across key policy areas.
Mayor of Newham Sir Robin Wales said: "This conference has been a resounding success and demonstrates our boroughs joint commitment to releasing the true potential of this combined area.
"Devolution is clearly an important subject for these councils and today's discussions have revealed exactly why it is necessary.
"We will now look at identifying the asks we can formally agree between us. I look forward to exploring this further and building a case we can take to central government and the Mayor of London."
Cross-party body London Councils represents London's 32 borough councils and the City of London Corporation and has been lobbying for devolved powers for the capital for some time. Members believe that fiscal devolution can better prepare councils for the challenges ahead.
London Councils' transport and environment committee chair councillor Julian Bell, who is also leader of Ealing Council in west London, told Horticulture Week in November that he does not know how local authorities will "square the circle" of further budget cuts over the next five years - after already cutting "low-hanging fruit" - without seriously damaging services.
He said: "There's a real danger that parks will deteriorate and that's the real worry. I'm not sure how it's going to look. It's a very worrying time of change."