The Dail and Seanad will have to sit in the Convention Centre at a cost of €50,000 per day because it would be unconstitutional to have virtual sittings during the coronavirus restrictions, TDs have been told.
Taxpayers will foot the bill for TDs and Senators moving to the 8,000-seater event venue on Dublin's North Wall Quay.
It comes after Oireachtas authorities were told virtual sittings, where some politicians would appear via videolink, would be unconstitutional as they would not be covered by parliamentary privilege.
Several Dail sittings of 50 or fewer TDs have taken place in Leinster House in recent weeks., but all 160 TDs will have to be present for the vote to elect a new Taoiseach and for sittings on budget matters and possible other legislative changes in the coming months.
Ceann Comhairle Sean O Fearghail said it is now expected there will be a number of sittings in the Convention Centre, as long as social distancing is in place.
The Seanad will also use the venue when up and running.
A number of TDs have questioned the Dail business committee's decision to approve the plan in recent weeks.
Mr O Fearghail acknowledged to the Herald that there is a "significant cost" involved.
"It's a huge cost, but there is a cost involved in every sitting in Leinster House as well," he said.
While the Oireachtas has said there is no cost for hiring the centre, there will be an initial €110,000 once-off cost to equip its auditorium with microphones as well as broadcasting costs.
Each sitting day will then cost approximately €50,000, raising the prospect of a substantial bill if the Dail sits there several times this year.
In an email to Fianna Fail TD James Lawless last Friday, the Ceann Comhairle ruled out virtual sittings, saying: "The advice is that the virtual sitting facilitated by the IT system would be radically different to the type of parliamentary assembly authorised by the Constitution."
Mr O Fearghail said the legal advice was that politicians would not "benefit from immunities in respect of utterances" outside of Leinster House.
"Mindful of the need for social distancing at present, the Business Committee has approved that the Dail will sit in the Convention Centre Dublin when there is a need for all 160 members to be present, such as for the nomination of Taoiseach and members of the Cabinet, estimates, legislation, etc," he said in his email.
Mr Lawless said the Dail should be able to pass legislation or update standing orders to get around the constitutional issues.
"I think a hybrid model, with some members present, and others participating online may cover all bases and it may allow us to save significant, unnecessary costs."