A controversy over Dublin Bus's adding extra buses to routes where it competes with private operators has escalated, following a decision of the Competition Authority to re-open an investigation into the issue.

Earlier, it emerged that research by the Department of Transport shows Dublin Bus has been running routes which were not authorised by the Government in competition with private operator Circleline.

Minister for Transport Noel Dempsey has described this as predatory behavour. He said legislation was planned by the end of year to stop the activity.

The Progressive Democrats want the board of Dublin Bus to be dismissed if the practice continues. But the bus company claims it has done nothing wrong.

Last month Circleline went into liquidation, citing unfair competition from Dublin Bus. Circleline ran buses from Lucan and Celbridge through the Dublin city centre to Rathfarnham. It said that from the start of its services in 2002 Dublin Bus saturated its routes with buses.

A Freedom of Information request by RTÉ News shows the Department of Transport monitored activity in the area. It found morning services by Dublin Bus almost doubled on the routes operated by Circleline.

Officials said Dublin Bus services did not comply with its own timetables and operated auxiliary services on a permanent basis.

The Department wrote to the state bus company on eight occasions warning it was operating unauthorised services. Dublin Bus responded saying its interpretation of legislation differed from that of the Department. In a statement, Dublin Bus today said it was fully compliant with authorisations for bus routes.

Meanwhile, the Joint Oireachtas Committee on Transport says there is a lack of urgency and co-ordination between the various bodies when it comes to tackling Dublin's congestion problems.

Publishing a short term action plan - Developing an Efficient Bus Network for Dublin - the committee outlines the best way to increase bus usage in the city ahead of the planned expansion of rail and light rail projects.

The report recommends that the current fleet of buses be expanded by an additional 350 vehicles, including sub-contracted vehicles. It also says that high priority routes and cross city centre routes should be designated to ensure reliable and efficient services. Improved links between the bus system and other forms of transport, especially the Luas, is also strongly encouraged.

The report calls for buses to be allowed use the Dublin Port Tunnel, as well as the expansion of quality bus corridors beyond the city to commuter counties.

The committee also want a bus gate at College Green, as recommended by the Dublin Transportation Authority, and a temporary bridge structure between Hawkins Street and Marlborough to reduce journey times, pending the building of permanent new bridges.

'Traffic capacity of the Dublin road network was reached 15 years ago,' commented Frank Fahey, Chairman of the transport committee.

'Today after unprecedented economic growth, the pressure on the network has increased by 300% but little additional road capacity has been provided. It is more necessary now than ever that we encourage a greater number of Dublin's commuters to use buses,' he added.