Chairwoman Ms Justice Mary Laffoy said at the weekend she is investigating a claim by the Pro-Life Campaign that an assembly member has been expressing pro-choice views on social media.
The first issue which the assembly will examine is whether the 1983 amendment to the Constitution on abortion should be repealed.
Ms Laffoy warned the body’s integrity could be undermined if the allegation proved to be true.
The inaugural meeting of the citizens’ assembly took place at Dublin Castle on Saturday.
Membersdecided to hold four weekend-long meetings on the constitutional restrictions on abortion before submitting a report to legislators.
The 99 ordinary assembly members, chosen by polling company Red C to be broadly representative of the electorate, joined Ms Laffoy and Taoiseach Enda Kenny at the meeting.
Other than the Eighth Amendment, the assembly has been mandated by the legislature to report on the country’s ageing population, fixed-term parliaments, referendums, and climate change.
Ms Laffoy told the assembly abortion is the particularly sensitive and contentious issue before them and pledged that openness will be an underlying feature of their work on all five of the topics they will discuss over the coming year.
An Oireachtas committee will discuss the assembly’s findings next year. Ms Laffoy said she will probably be calling for submissions on the Eighth next week.
Thanking the members for participating, Mr Kenny said the issues they will discuss are “beyond party politics”.