Politicians and trade union officials have urged rail bosses to 'get a grip' after chaotic scenes at London Bridge Station during Tuesday evening's rush hour.
Network Rail said that it closed the doors to the station on Tuesday evening on the advice of the British Transport Police after train services were disrupted by a person on the tracks near Streatham Common.
Photos were posted on social media of frustrated passengers vaulting over the ticket barriers to reach their trains.
"I understand how difficult last night was for many of our passengers and they showed great patience and understanding in what was a very tough situation," said Dave Ward, Network Rail's route managing director for the south east.
"The railway around south London is so busy that if one train is delayed by just one minute it will delay 17 other services as a result. That is why the Thameslink Programme is so important to the future of our railway.
"At peak time, the effect of closing the railway even for 45 minutes has massive effect and we have to manage our stations carefully to help get people home safely.
"We will as a matter of course be reviewing our plans and the events of last night to see what, if any, lessons can be learned."
Simon Hughes MP said: "The chaos and confusion we yet again saw yesterday at London Bridge is totally unacceptable. I am extremely concerned that if Network Rail does not get a grip then we could see passenger safety put at risk.
"I have been reassured repeatedly by senior managers that they have the situation under control but it is increasingly clear they do not.
"The chief executive must consider very seriously if he has the right people in place to take forward this vital investment and redevelopment while keeping services running and passengers safe."
Val Shawcross, London Assembly member for Lambeth and Southwark, said: "Last night we returned to the disastrous days of chaos we experienced earlier this year. We were promised these scenes of total disorder were behind us, but last night's meltdown shows serious problems remain.
"It is simply not acceptable for the government to sit idly by whilst commuters, some paying thousands of pounds each year in ticket costs, are left stranded on dangerously crowded platforms, unable to get home.
"Why is the secretary of state not here talking to passengers, talking to staff, and putting some support in place for Network Rail and Southern Rail who are clearly struggling to cope?
"There needs to be a very frank discussion with rail bosses about why the rail service has been consistently underperforming while passengers are charged extortionate amounts for the privilege of using a poor service.
"We also need swift action from the Government to deliver the reliable rail network that was promised earlier this year and that we've yet to see."
Mick Cash, general secretary of the RMT union, said: "The fragmentation and privatisation of our railways leaves train companies and Network Rail blaming each other while passengers and staff are left caught in the kind of life threatening chaos we have seen in pictures from one of London's major rail terminals last night.
"Those pictures shame our railways and it is about time those in control, including the Government, started to take some responsibility.
"The bottom line is that we are trying to cram more and more passengers into a transport system which is already at bursting point and where the pressure is on to cut more corners and axe more staff in the drive for profit.
"It doesn't take a genius to work out that that the poisonous cocktail of surging demand against a background of cuts leads to the kind of horrendous meltdown played out at London Bridge in yesterday's evening rush hour.
"RMT is demanding action before this chaos becomes a tragedy."
For the latest local news and events direct to your inbox every Monday, you need our weekly email newsletter SE1 Direct.
7,000+ locals read it every week. Can you afford to miss out?
Read the latest issue before signing up