The number of TDs in the Dáil is expected to be reduced by eight to 158 on the recommendation of the Constituency Commission, which is due to report next month.
The commission will recommend wholesale changes to boundaries, with Dublin, Munster and Connacht-Ulster each losing three seats and Leinster outside Dublin gaining one.
The changes will cause upheaval in all parties, particularly when taken in tandem with the fresh legal requirement that each party must nominate women as 30 per cent of its candidates in the next election.
The commission was charged with redrawing constituency boundaries. It took into account the 2011 census figures published in March and the Coalition pledge to reduce the number of TDs.
Its terms of reference provide for a minimum of 153 TDs in the next Dáil and a maximum of 160. There are 166 TDs in this Dáil.
It is understood that the commission has almost completed its work and its report will be published in the middle of next month.
The reduction of three seats in Munster will come about through consolidation of the two three-seat constituencies in Kerry into one five-seater. The same process will take place in Tipperary, where one five-seat constituency will replace two three-seaters.
Cork will also lose a seat, with the likelihood of Cork South Central being reduced from a five- to a four-seater with readjustment of a number of boundaries in the surrounding constituencies.
The three-seat reduction in Connacht-Ulster will come about through merging two Donegal three-seaters into one five-seater and the five-seat Cavan Monaghan being reduced to a four-seater.
The third seat in the region to go will be in either Galway or Mayo, with the eastern portion of one of those counties being merged with Roscommon. In tandem with that, the old Sligo-Leitrim constituency will be restored, ending the partition of Leitrim for electoral purposes.
The reduction of three seats in Dublin will be achieved through extensive changes to boundaries. Two seats are likely to go on the north side of the city, with an extensive redrawing of constituencies like Dublin North Central, Dublin North West, Dublin Central and Dublin West.
One seat is expected to go on the south side, with the most likely outcome being the reduction of Dublin South Central from a five- to a four-seater. But there is also a possibility that Dún Laoghaire could be reduced from a four- to a three-seater.
Laois-Offaly is certain to gain a seat in the revision, with the current five-seat constituency being broken up to form two three-seaters.
The census showed that the existing Laois-Offaly constituency has the highest ratio of population to Dáil deputy at 30,565, followed by the three-seat Kildare South and the four-seat Kildare North, which are marginally over the 30,000 limit.
Both of those constituencies are likely to lose territory as a result.
Speaking in Midleton, Co Cork today, Taoiseach Enda Kenny said the commission was "completely and utterly" independent and declined to comment on the contents of the report.
"I have no idea what is in the report and I am going to make no comment on it good, bad or indifferent until I see it. This is one commission of a number that is quite utterly independent in terms of its views."
Minister for Agriculture Simon Convey said he has been advocating a reduction in TD numbers for a long time. "I have no problem with reducing the number of TDs," he said. "I think it makes sense. And if that means there are changes in my own constituency, then so be it. You cannot be precious about these things."
According to article 16 of the Constitution, the ratio of population to TD has to be between 20,000 and 30,000. While in opposition, Fine Gael leader Enda Kenny pledged to cut the size of the Dáil by 20 seats to 146, but that would require a constitutional referendum as it would have left a ratio of more than 31,000.
With 158 TDs, the ratio would be 29,039, the closest to the limit since the adoption of the 1937 Constitution.
For much of the State's history that ratio was close to the 20,000 figure in order to maximise the number of TDs in the Dáil. However, the rapid rise in population combined with reduction in the number of TDs means that the new ratio will involve the lowest number of TDs to population.
The commission accepted submissions from interested parties, including TDs, in addition to census data, in arriving at its decisions.
The five-person commission is chaired by High Court judge Mr Justice John Cooke. The other four members are: clerk of the Dáil Kieran Coughlan; clerk of the Seanad Deirdre Lane; Ombudsman Emily O'Reilly; and secretary general of the Department of the Environment Geraldine Tallon.