London mayor Boris Johnson has met with rail bosses to discuss the travel disruption at London Bridge station.
The mayor said he shared the frustration of those who have experienced delays and Network Rail were “very apologetic”.
The station is being rebuilt for the Thameslink Programme.
Network Rail admitted the problems were “unacceptable” and “embarrassing” and stemmed from a timetable that did not fit the new infrastructure.
‘Months of misery’
Passengers have complained that delays and cancellations were causing “dangerous levels” of congestion on the concourse.
Mr Johnson met with the Network Rail executives and Department for Transport representatives on Thursday afternoon.
Following the meeting he said: “This is a vast project….It involves the total rebuilding of the oldest commuter railway station in the world.
“There will inevitably be disruption from these huge improvements, but they have reassured us that they are straining every muscle to keep that disruption to an absolute minimum.”
BBC London’s transport correspondent Tom Edwards said the new infrastructure – the platforms and signalling – could not cope with the number of trains so the timetable was having to be amended.
He said what would worry commuters was that this was just the start, with years left of work at the station.
Rail Minister Claire Perry said: “We’ve got an amazing piece of work going on down there at London Bridge.
“We’ve got £6.5bn worth of investment in the Thameslink programme, a brand new station replacing what’s there, but it’s completely inexcusable during that process to inconvenience passengers to this extent.”
Network Rail apologised for the disruption.
Dave Ward, Network Rail South East route managing director, said: “We thought we would be presenting a new station and a new method of operation after several months of misery leading up to it and that hasn’t happened and I’m deeply regretful for it.”
It has also emerged that a fare glitch when ordering rail tickets online meant some passengers could be overcharged.
Sevenoaks Rail Travellers Association found that some firms’ websites had not updated their systems to take into account the changes to the routes for engineering works at the weekend, meaning travellers have to go to Victoria rather than London Bridge.
The fare should include the cost of an Underground pass to London Bridge whereas some websites are charging extra.
A spokesman for Southeastern said: “We’re aware of an issue regarding fares for journeys beyond London Bridge station this coming weekend and are working with industry colleagues to fix this as quickly as possible.
“In the meantime, we advise any passengers who have already booked tickets to travel during this period, and have paid the higher fare, to get in touch with our customer services team and we’ll arrange a refund.”
Network Rail is set to publish an internal report on Monday into Christmas engineering work which overran, leading to the closures of King’s Cross and Finsbury Park stations on 27 December, and the partial closure of Paddington station on the same day.
The Office of Rail Regulation is also holding an inquiry into the overrun which Transport Secretary Patrick McLoughlin described as “totally unacceptable”.