The latest electoral register, published this month, could be wrong by up to 860,000 voters, a Sunday newspaper has claimed.
This is in spite of efforts by the Department of the Environment to improve the voter database.
According to figures obtained by the Sunday Tribune, there are almost 3.1 million people registered to vote in this country.
That's almost 300,000 more than the number of people actually eligible to vote.
In addition, the international norm for voter registration is 80-85% of the population - which would mean the level of inaccuracy would be about 800,000 voters.
The Department of the Environment undertook measures last July in an effort to improve the register's accuracy, but opposition parties now say the situation is getting worse.