Councillors voted for the additional member system which could see the number of Labour councillors halved and gains for the Conservatives, Liberal Democrats, Green Party and other groups.
The system mirrors the one used in the
Scottish Parliament, Welsh Assembly and Greater London Assembly.
Lewisham chief executive Barry Quirk commissioned a public policy group, made up of academics from University College London and the London School of Economics, to look at alternative ways of carrying out local government elections.
He said: 'We commissioned a report from national experts on election systems and they looked at data from Lewisham in previous elections. We are now discussing the practicalities and time-scale of introducing proportional representation with the DTLR.'
The report said the voting system in Lewisham is unfair. Labour won just over half the votes in 1998, but claimed nearly all the seats.
It said: 'At present the voting system does not work fairly. The Labour Party wins a clear majority of votes, but then gains virtually all the seats. Other parties are under-represented, even the Conservatives and Liberal Democrats which elect too few councillors to form an effective opposition group.'
The council cut its number of councillors from 67 to 54 before the local elections
in 1998 and 50 of these are Labour, with one Conservative and three Liberal Democrats.
The Conservatives would have won 11 seats under proportional representation with the Liberal Democrats gaining two
If the government gives the go-ahead
to the plans the additional member system could be introduced in time for the May local elections.
Proportional representation could be introduced at Lewisham with minimal cost and ward boundaries would not have to be redrawn, according to the report.
A spokeswoman for the DTLR said: 'This is all very confusing. We don't know anything about this plan. We need to discuss it with the council.'