Fine Gael has proposed removing the M50 barrier at peak times as part of a series of measures to tackle traffic problems in the greater Dublin area.
The party has also said it would provide a further 100 new buses to Dublin Bus in addition to the 100 promised last month by the Government, along with 100 private operator licences for new bus routes.
Further private operator licences would be issued for school bus routes, the party promised.
However, Fine Gael leader Enda Kenny has rejected suggestions that its proposal for significant competition in the Dublin bus market was at odds with the policy of Labour, its potential coalition partner, which has opposed privatisation on any existing Dublin Bus routes.
He said the Government had failed until the last month to provide either funding for Dublin Bus or licences to private operators for the additional services needed for the increasing population around Dublin.
"They spent €40 million on bus corridors but provided no buses to run on them," he said.
Mr Kenny cited the example of one Lucan-based couple, whom he visited at 6.30am yesterday morning to hear about the amount of time they spend in their car every day because of a lack of public transport.
"Dominic and Catherine Price and their three-year-old daughter Heather told me how they spend the equivalent of a combined 3½ working days [ a week] in their cars travelling to and from the creche and work," he said. "Their case epitomises 100,000 other cases in the Lucan area."
Fine Gael transport spokeswoman Olivia Mitchell said the experience of Lucan residents was replicated "right around the M50".
"You cannot cross the M50, you cannot move on the M50," she said. "The M50, instead of liberating us, has become a wall around the city."
Ms Mitchell said her party was committed to a liberalisation of the bus market in the capital to allow competition on bus routes. "Let the market decide how many buses are required," she said.
Mr Kenny dismissed suggestions this would be at odds with Labour's policy. "We are talking about licensing operators for new routes where there are currently no services," he said.
Yesterday, Minister for Transport Martin Cullen tried to highlight the differences between the Opposition parties.
"Fine Gael has a totally different stance on buses than Labour," a spokeswoman for Mr Cullen said. "Party collaboration on this issue is not evident. They are worlds apart."
Mr Cullen also defended the Government's record. "The Government has committed €529 million in bus expenditure for the greater Dublin area under its programme for investment in Transport 21. A further €599 million has been provided for traffic management measures," said the spokeswoman.