The Russian Unity Party, one of Estonia's smallest political parties, has listed more than 60 individuals as members, including one high-ranking official from another party, who never applied for membership.
The erroneous names were discovered in the party's membership rolls after they were published on its Web site.
Leho Karjus, secretary general of the Pro Patria Union party, said he was shocked when he found out that he was on the list. His entry included his correct birthday.
"I have absolutely no idea how it happened," he said. "They called me and apologized, but I have no idea if they have actually removed my name from the list because the person who has the lists can't be contacted."
The errors have called into question the party's entire membership structure.
The Russian Unity Party was established in 1998 and is currently involved in leadership squabbles that have led to court proceedings.
It has 1,314 members, according to the list published on the Internet.
But that list contains a number of inconsistencies. It shows that several members joined the party in December 1997, though the party wasn't formed until six months later.
In addition, 40 members are listed twice.
Alfrida Liivak, the party's deputy chairman, admits the list is disorganized and said it would be updated as soon as possible. But the law suit, which was brought by one party to challenge the leadership of another leader, will delay updating.
The court proceedings have also prevented access to the party's membership applications.
Estonian law requires a minimum of 1,000 members for a party to be registered.
An application can be written on any type of form but must include the full name and personal code of the applicant. The party must then submit the list of members to the National Business Registry once a year where they remain public.
No officials would comment on whether the Russian Unity Party may have fraudulently added people to its party list who weren't members to qualify for registration.
Karjus said he would take no legal action against the party. The legitimacy of the party's membership list will be its biggest concern, he said.
Estonia currently has no laws against falsifying party lists, according to the Tallinn City Court.
Earlier this month a reporter at the daily newspaper Eesti Ekspress found herself included on a party member list produced by the Center Party, which she supposedly had joined a few months earlier without her knowledge.
A handwriting expert later proved that the signature on the application form was not hers.