On Tuesday, one of the victims told the party they had reported the incident to police.
And on Wednesday, police said they had launched an investigation into the alleged assaults.
Kirton said he had also been contacted by another victim, who said she had been subjected to a similar assault at a Labour event in the past 10 years.
Kirton and Ardern both acknowledged the party had been too slow, and not explicit enough, in its offer of support to the victims.
Ardern said the party had failed