Transport bosses were warned of a "crisis situation" facing the Luas cross city line months before it opened.
The extension is being blamed for bringing traffic to a standstill around College Green.
Dublin Bus have been forced to divert nearly 30 routes away from the area as a result of the recent surge in traffic congestion.
The Sunday Business Post reports that transport officials were warned as early as September that test runs had led to traffic jams and delays.
Despite the warnings, the €368m line was opened was launched as planned in December.