The public hearing into an alleged breach of the Ethics in Public Office Act by Fianna Fβil TD, Mr Ned O'Keeffe, begins this morning.
The inquiry is the first public examination of a politician under the ethics legislation.
The allegations concern Mr O'Keeffe's declaration under the Act, in relation to his Co Cork pig farm. He resigned as a minister of state at the Department of Agriculture in February.
The commission recently defended the 11-month delay in holding the hearing. The Labour Party leader, Mr Ruair∅ Quinn, wrote to the commission expressing serious concern over its failure to hold a hearing in regard to the complaint he made in December last, under the terms of the ethics legislation.
The commission pointed out it was the first such hearing and said it was disappointed that, to date, it had not been possible to proceed to a formal hearing.
"It has always been the intention of the commission that the investigation would be completed in the least possible time.
"However, it is of the utmost importance to the commission that its procedures in conducting the investigation should comply fully with requirements of constitutional and natural justice."
It is understood the commission has been conscious of possible legal challenges.
Mr O'Keeffe, who was minister of state at the Department of Agriculture, voted against a Labour Party private members' motion last November, calling for a ban on the feeding of meat-and-bone meal to all animals.
However, Labour says he should have declared in advance that his family farm had a meat-and-bone meal licence, and that he therefore had a material interest in the vote.
The Ethics in Public Office Act requires that such a material interest be declared to the Public Offices Commission in advance of any vote.
The inquiry will be chaired by the POC chairman, the ombudsman, Mr Kevin Murphy.