The politicians said they were worried that government plans to centralise the control of benefits from new developments would reduce the amount of money which currently goes to local communities across the capital.
Collected and disbursed by the Treasury, the new planning gain supplement (PGS) tax would be used to fund infrastructure around the UK rather than in the area where the tax is collected - a situation the assembly feels is unfair.
The assembly's Planning and Spatial Development Committee (PSDC) has now written to the government expressing concerns about the plans to scale back the local planning obligations system.
Under existing laws, the organisation points out, local authorities work with developers to ensure major building schemes do not disadvantage the local community.
Planning consent hinges on agreements obliging developers to provide transport improvements or new community facilities.
The proposed alternative, a tax collected and distributed centrally, would remove the power of local negotiation at the expense of London's communities.
'Londoners will probably end up funding development for the rest of the country with little in return,' said Tony Arbour, chair of the PSDC.
'We are concerned that once again London will lose out to the rest of the country, and these views are shared by the Association of London Government.
'We must make sure that development in London continues to be linked to community requirements.'