The spitting ban would only come into force after approval from the government
The transport and environment committee of umbrella group London Councils has approved £80 fines for spitting in public places.
Policing and issuing fines through the by-laws will be the responsibility of individual councils across London.
The Department for Communities and Local Government has yet to approve the measure.
The move towards a London-wide crackdown comes after action was taken individually by borough councils.
People are likely to be allowed to spit with "reasonable excuse" or into a handkerchief, tissue, bin or other receptacle.
In November last year Communities Secretary Eric Pickles approved an Enfield Council by-law making spitting an offence, punishable by fines up to £500.
Waltham Forest and Newham councils have already been issuing fixed penalty notices for public spitting.
Waltham Forest has been using existing powers to issue fixed penalty notices since February 2013.
The approval from London Councils followed a public consultation which showed people "overwhelmingly in favour" of a fixed penalty, according to the council group.
