The rail regulator is to investigate the disruption caused at two major London stations due to over-running engineering works after Christmas.
There was major disruption at both Kings Cross and Paddington over the weekend leading to passengers being stranded and severe overcrowding at Finsbury Park station, following the closure of Kings Cross on Saturday.
The Office of Rail Regulation has said it will investigate what went wrong on the rail network after Christmas.
Transport secretary Patrick McLoughlin is also to ask track operator Network Rail how further similar problems can be avoided in the future. He added that he expected affected passengers to receive compensation.
Robin Gisby, managing director of network operations at Network Rail, apologised for the “upset and upheaval” suffered by passengers over the weekend.
"We now move our focus to completing the handful of other projects still underway without further impact on passengers,” he added.
“We will also begin our investigation into what went wrong with the work at Holloway (north of King's Cross) and the planning that went into this project."
King’s Cross reopened on Sunday while services also returned to normal at Paddington on the same day.