Newshub understands Immigration Minister Iain Lees-Galloway is at the centre of the allegations raised by National leader Judith Collins on The AM Show.
Lees-Galloway, a Labour MP, was due to be interviewed by Newshub at 10.30am about cannabis workplace testing but pulled out just minutes before.
His Facebook page and Twitter have been deleted.
The Prime Minister has called an impromptu press conference at 11am on Wednesday and her office provided no details about what will be discussed.
It came after National leader Judith Collins told The AM Show on Wednesday morning that she had passed on to Ardern a tip-off she had received about a Labour Party minister.
"I have advised the Prime Minister and I have asked for anybody who has that information to send it directly to her," Collins told The AM Show. "I am not going to be indulging in any attacks on Labour on these things."
She told RNZ it involved "fairly inappropriate behaviour".
Collins said she asked to speak to the Prime Minister on Tuesday after Question Time in Parliament and said that's when the information was passed on.
"I asked to speak to her and I said I had received such a tip off and I did not want to receive any information on it. I would be asking the person to send it directly to her.
"She has provided me with an email address for that and that has been passed onto the person who contacted me. I don't want to engage in this."