Fianna Fail leader Micheal Martin has accused Sinn Fein of preventing the people of Northern Ireland from having a voice in the Brexit negotiations.
Mr Martin warned that "historic damage" to the region is being threatened by Brexit but said that the pro-EU majority in the Stormont Assembly is being stopped from being heard because Sinn Fein "is refusing to allow the institutions to be re-established."
Stormont has been without a powersharing government since January when the former Deputy First Minister, the late Martin McGuinness of Sinn Fein, resigned over the DUP's handling of a botched green energy scheme.
Talks between the two largest parties, the DUP and Sinn Fein, have so far failed to break the deadlock.
Speaking at the Fianna Fail think-in conference in Longford on Monday Mr Martin said it is "long past time" for the Stormont institutions to be restored.
"So far this island's most consistently anti-EU party Sinn Fein is holding to the obviously cynical position that while the threat of Brexit is a threat to every element of the peace settlement but that no one is allowed to do anything about it," he said. Mr Martin raised concern over "the current state of Brexit negotiations".
"Obviously the shambles in the government in London is the biggest problem.
"However, we believe that our Government must start being far more active and ambitious in its proposals.
"Saying that we won't help the British design a border is all full and well, but when will there be an actual proposal for what our government believes should happen?" he said. The Cork South Central TD again insisted that a special economic zone should be developed for Northern Ireland and the border counties. He said this could help cross-border connections and allow priority measures to help develop disadvantaged areas.
Meanwhile, Mr Martin accused the Irish Government of failing to deliver on housing and health.
He said the Taoiseach needs to commit to getting more people housed and getting children out of emergency accommodation in hotels.
Mr Martin criticised former Housing Minister Simon Coveney for not choosing to stay in that department to tackle the problem.