More staff, an improved timetable and better delay warnings for passengers, have been promised by Network Rail to tackle London Bridge station chaos.
Rail minister Claire Perry said changes would take place immediately, following talks with MPs.
Disruption has followed rebuilding work involving the £6.5bn Thameslink Programme.
The Rail, Maritime and Transport union has said delays and overcrowding have led to “life-threatening chaos“.
Ms Perry said it was right to invest in Thameslink but the disruption for passengers was “too great”.
She said carrying out work on one of the UK’s busiest stations was like doing “open heart surgery on a marathon runner”.
“[But] what you have to do in that process is make sure people who are using that station every day to get to work, to get home, who want to be home to relieve the nanny or to see their kids, actually have a reliable service,” Ms Perry said.
She said former London Underground chief operating officer Phil Hufton was made gold commander for the station, a new station plan had been formed, and Southern rail operator had a new timetable to give people predictability and reliability.
Ms Perry said compensation for passengers was being looked at.
Mr Hufton, who is now Network Rail’s managing director of network operations, said: “In the last few weeks passengers have experienced unacceptable levels of service and over-crowding at London Bridge station.”
He said passengers had been tolerant but had understandably lost their patience and measures being put in place would improve services and station management.
MPs who met Ms Perry and Transport Secretary Patrick Mcloughlin on Wednesday had said dangerous overcrowding had caused a knock-on effect on the transport system and it was only a matter of time before someone was seriously injured.