Earlier today Prime Minister Jacinda Ardern, when asked about calls for a Royal Commission, said she didn't want to double up on WorkSafe and the Coroner's investigations into the disaster.
"We will get the answers that we need and what the community wants and needs as well."
But Collins said Ardern "may wish" to wait for the findings of those investigations, but should "tell the people involved and the families why that is".
Collins said if a Royal Commission hadn't been announced, she would announce one at the start of the term if she were elected to be prime minister.
Collins compared Whakaari to the Pike River Mine explosion which killed 29 people and was examined by a Royal Commission after a WorkSafe investigation.
Collins said the magnitude of the eruption warranted a Royal Commission.
"I think people want answers. People want answers about how this was able to happen and they also want answers about the responses to it.
"[People] are very concerned that there may not be as robust an investigation as they would expect."