The plan by the Minister for Transport to increase speed limits in 43 locations across the State runs against the Government's road safety strategy, the Green Party said today.
Mr Brennan has threatened to remove the power from local authorities to set speed limits on national roads in their areas if limits are not increased in the specified locations.
It emerged today that Mr Brennan's Department has prepared a preliminary list, which is being sent to local authorities around the country, earmarking stretches of road where it believes the speed limit may be too low.
Green Party transport spokesman, Mr Eamon Ryan, said: "On certain of the national roads I can understand why the speed increases may be justified but certainly in the case of the three changes Brennan is recommending for roads within our shared Dublin-South constituency I would reverse each of the increases that the Minister has proposed.
"Higher speeds on the Dundrum bypass will do nothing to improve the congestion that is the real problem for motorists in the area. Raising the speed limits on the Braemor road is disgraceful given that it is clearly a residential as well as a distributor road.
"The famous case of the Belfield flyover should be seen as an example of how rigorous enforcement can change driver behaviour," he added.
Mr Ryan said it was "remarkable" that Mr Brennan had recently ruled out the introduction of a 20 mph speed limit on residential roads, which is commonplace in most other European countries.
"The support for this move from bodies such as the AA and the Society of the Irish Motoring Industry shows how powerful the motoring lobby is in this country. Until we have a similar lobby for road safety we are never going to reduce the carnage on our roads".
The Labour Party's spokesman on transport, Ms Roisín Shortall, warned Mr Brennan that threatening local authorities with removing their power to impose speed limits was "risky".
"Local authorities are best placed to judge on setting speed limits on stretches of road that are notorious in that area for being dangerous or accident-prone. Stripping local authorities of this power would jeopardise safety on local roads," she said.
