The Brent Cross Railway would link the massive new Cricklewood/Brent Cross regeneration scheme, expected to gain planning permission this year, with Brent Cross Underground station and a proposed Thameslink station.
The light rail link would then use an existing "under used" railway line from Neasden to Harlesden owned by Network Rail.
Later extensions could see the line stretch down to North Action and Park Royal connecting with other lines to provide a key orbital route for London.
The project, that would be similar to the Docklands Light Railway, has been conceived by local resident John Cox who has teamed up with the Campaign for Better Transport.
The proposal has been sent to Barnet and Brent Borough councils and Transport for London. It is hoped that public cash will be made available to fund a detailed and feasibility plan.
However, a spokesman for the developers Multiplex, Hammerson and Standard Life Investments, claimed that existing public transport plans for the site would be adequate.
"Our transport plans are already comprehensive and will bring the greatest investment in new transport infrastructure in the area's history – all privately funded," said the spokesman.
"Our detailed transport modelling has shown the new facilities will handle the increase in the number of people visiting the area in the future."
Meanwhile, Network Rail and developers Delancy and Land Securities have unveiled plans for a two 127m residential towers above Clapham Junction rail station in south London.
Under the £400M scheme, access to the 17 platforms would be improved.