Fine Gael and Labour had vowed to reopen a 25-year-old investigation into the killing of Fr Niall Molloy after reviewing files on the case.
Alan Shatter and Pat Rabitte, justice spokesmen for the opposition parties added that the murder case would be a priority if they were in power after the next election.
Father Molloy, a Roscommon priest was beaten to death in home of his friend in Clara, Co. Offaly, in 1985. The murder occurred following the lavish wedding of Mr Flynn's daughter.
The postmortem on the priests body showed that he had endured a violent death and had died as a result of swelling to the brain after receiving multiple blows to the head.
A year after the Roscommon man's death, Mr Flynn stood trial for his manslaughter but Mr Justice Frank Roe acquitted him after less than four hours of deliberation, on the grounds that the priest could have died from a heart attack prior to the vicious assault.
Some time later it emerged that the judge knew Richard Flynn and was therefore not authorized to have heard the trial.
A second inquest found that the priest had in fact died as a result of his head injuries.
The family of the late Fr Molloy are said to be overjoyed by the opposition's pledge to reopen the case.