In its response to the draft strategy, the watchdog says capacity is the biggest issue facing rail travel in London and the south east and calls for a 30 year vision.
This plan should should examine the major changes and investment needed to transform the network. It says that upgrading to network to 12-cars and increasing train frequency is central to this.
Passenger Focus chief executive Anthony Smith said, "These plans are making the best of the resources available but it is a last ditch attempt.
"The system is already at capacity and it is vital that the industry invests for the future to ensure it can accommodate the increased capacity".
Passenger Focus interviewed 25,000 people travelling into and out of London. They said that they want more room to sit and stand on trains, and not stand for more than 20 minutes.