Bank Tube station in the City of London could be re-tunnelled as part of a planned revamp.
London Underground (LU) said the refurbishment work would "relieve congestion and provide step-free access to the Northern line platforms".
If approved, work could begin in 2015 and finish by 2021, LU said.
About 300,000 passengers a day use the station, which is served by the Central, Northern, Waterloo and City lines and Docklands Light Railway.
LU said the proposals were made after a 43% rise in passengers using the station in the last few years.
Plans include a new entrance on King William Street, re-tunnelling on the Northern line, installing lifts to provide step-free access and spacious interchange passageways.
Richard Parry, LU's strategy & commercial director, said: "Currently the Northern line platforms at Bank in particular suffer severe congestion during morning and evening peak times, which will get worse as passenger numbers grow.
"If this work is not carried out station control measures, such as restricting access at busy times and non-stopping trains, would have to be implemented even more frequently than today."
Work has begun on a new ticket hall and a new entrance onto Walbrook which will provide a step-free access from the street to the Waterloo & City line. The work is due to be completed in 2015.