1,300 ads on Facebook related to the Eighth Amendment referendum campaign have been captured by the Transparent Referendum Initiative since its launch in February.
405 of the ads were collected in the past week alone and in total there have been 280 unique advertisers recorded.
The TRI was set up to highlight the absence of regulation around online political campaigning ads.
Its 600 volunteers have used the Who Targets Me tool over the past number of months to collect referendum related ads that appear on their Facebook accounts.
In its final analysis prior to polling day TRI says the 1,300 ads captured represent a fraction of all the advertising purchased on Facebook during the period.
It says no complete data on the extent of advertising and the amount of money spent has been shared by Facebook.
Two weeks ago Facebook announced it was banning ads related to the referendum that were coming from overseas, while Google announced a pausing of all ads connected with the campaign.
However, TRI says it has collected screengrabs of political ads that have appeared on a range of platforms since then, including on international news sites, gaming apps, streaming services, Spotify and an academic bibliography generating site.
Of the almost 1,300 ads collected by TRI, 749 were associated with Repeal and 532 were on the Retain side.
Only 38% of the advertisers are registered with SIPO or associated with registered groups.
79% of the groups not registered with SIPO are Irish, 9% are from advertisers based outside of Ireland and 12% are untraceable.
