Business leaders have revealed their proposed route for a £12bn Crossrail 2 train line spanning London.
The London First business group proposed the line would run from the south-west to the north-east of London
Under the proposals, the line would run from stations in Hertfordshire to parts of Surrey and open in the early 2030s.
In central London, it would pass through Euston, King's Cross, Angel, Tottenham Court Road and Victoria under London First proposals.
It is hoped the line would relieve the Victoria line and much of the Piccadilly and Northern Tube lines.
Crossrail 2 would be linked with walkways to connect Euston, King's Cross and St Pancras stations rather than building a new station.
London First created a working group in October 2011 to examine the case for the new rail link beneath central London.
It has examined current demand and congestion forecasts on the Underground after 2020 and assessed the impact on the system of new national projects such as HS2.
It claims without Crossrail 2, at least £6bn would need to be spent in incremental improvements to existing Tube and rail infrastructure, "offering a fraction of the benefits while still leaving London congested".
Former Transport Secretary Lord Adonis, who chaired the group, said it was a "compelling plan with strong business support".
London First chief executive Jo Valentine added that a decision had to be made fast as "we cannot afford the decades of indecision that delayed getting started on Crossrail 1."
The first Crossrail project was suggested in the 1990s however it was not given the go-ahead until 2007.
It is expected to go out to consultation in late 2013.
The report says employment in the capital city is projected to rise by 700,000 and the population is set to rise by 1.5 million to almost 10 million from mid 2020s onwards.
Transport Minister Stephen Hammond said: "As London grows we'll need continued investment in its transport network to accommodate this additional demand, and support continued economic growth.
"Crossrail 2 is certainly one of the options for doing this. I welcome the work done by TfL and the publication of London First's report and will now consider the points it raises."
London Mayor Boris Johnson said: "There is no time to lose and my team will work closely with London First and others on developing plans for this vital railway."
RMT union general secretary Bob Crow said: "It is vitally important that we don't waste more time delaying transport infrastructure developments that would make a massive difference for millions of people.
"It is equally important that big-business isn't allowed to call the shots on the routes and the timescales for these infrastructure developments.
"They should be built and operated in the interests of all Londoners not just the wealthy elite."
The first Crossrail project, currently under construction, will connect 37 stations from Heathrow Airport and Maidenhead in the west, through central London and out to Abbey Wood and Shenfield in the east.
Crossrail is due to be completed in 2018.