Bus Éireann's morning commuter and long-distance services are now up to one-and-a-half hours late and its timetable is at breaking point, according to the company.
The situation is similar to that faced by Dublin Bus, which earlier this week complained that traffic was backed up from St Stephen's Green to Walkinstown Roundabout.
The cost of traffic congestion to both companies is put at €47 million a year.
While Dublin Bus blamed Luas construction work for this week's difficulty, Bus Éireann said its problems were due to widespread and long-term congestion.
In a critical assessment of the effectiveness of the capital's bus lanes, traffic enforcement and the expansion of suburban Dublin into surrounding counties, Bus Éireann said delays and disruption would deteriorate further unless radical action was taken by transport authorities.
Bus Éireann, which currently hires buses from private operators to "inject into the system" as part of measures "to fill gaps in timetables" due to traffic congestion, said it could not sustain the rising cost of such measures, which it put at €13million a year.
The company is currently preparing a report which is expected to be critical of bus lanes, which it claims are inadequate at roundabouts - particularly at the M50 - and are haphazard in the city centre. The company also feels the bus lanes do not go far enough from the city centre to meet the start of the traffic congestion.
The company is critical of enforcement measures on the bus lanes, and has complained of the level of abuse. It said traffic congestion in a range of satellite towns such as Clane, Co Kildare, Edenderry, Co Offaly, Bray, Co Wicklow, and others has become chronic in recent years.
Commuter housing as far out as Arklow in Co Wicklow, Naas in Co Kildare, Kells in Co Meath and Drogheda in Co Louth has congested all approach routes to the capital .
According to Bus Éireann spokesman Mr Cyril McIntyre traffic congestion - partly due to road works - in north Wicklow has become so bad that the company's drivers are reaching the limit of their daily driving times while stuck in traffic.
According to Mr McIntyre, the problem begins early in the morning when buses based in satellite towns around the greater Dublin area head for the capital. After the morning peak these buses are then used for longer-distance services to the regions. But because of traffic delays accessing the city, the commuter services are "on average 40 minutes to an hour late" with a subsequent knock-on effect which delays regional services for up to an hour-and-a-half.
According to Mr McIntyre there are problems:
On the M/N1 at the airport because of congestion and the fact that the bus lane does not continue through the roundabout;
On the N3 because the bus lane begins at Blanchardstown while the congestion begins further out, towards Clonee, Co Meath;
On the N4 because the bus lane starts at the Spa Hotel and congestion starts further out in Leixlip and even Maynooth. On the outbound journey the bus lane still ends at the Foxhunter public house in Lucan, while the congestion continues out towards Kilcock;
At the M50/N4 junction inbound because the bus lane ends at the King's Hospital bus stop, forcing buses into the very busy junction without an enforced priority crossing system;
On the N7 which is congested as far as Rathcoole and where bus lanes need to be extended beyond Newlands Cross to Rathcoole;
On the N11 where traffic congestion in north Wicklow is chronic due to congestion in towns and road works along the route.
According to Mr McIntyre, the bus lanes need extension and greater enforcement. He also said inner city bus lanes needed to be improved, pointing out that the bus lane on the city quays was not constant along the quays.
