National's Pansy Wong is the latest MP to confirm helping Auckland millionaire Yang Liu get New Zealand citizenship.
Internal Affairs Minister Rick Barker confirmed on Friday that Mr Liu was being investigated for possible immigration fraud.
Mr Barker said the investigation could result in a prosecution and it was possible Mr Liu's residency would be revoked. If that happened, he could lose his citizenship.
Labour MP Dover Samuels has said he supported Mr Liu's citizenship application, which was granted in August this year.
Ms Wong issued a statement at the weekend saying she wrote a letter to the Department of Internal Affairs after Mr Liu told her he was concerned about delays in processing his citizenship application.
"I was unaware of the allegations that have been made against him in the media in the past day or so," she said.
"Because he had already been here for a number of years, I assumed relevant checks had been made by government officials."
Mr Liu appears to have spread his generosity evenly between Labour and National -- he gave both parties donations of $5000.
National's John Key confirmed yesterday he met Mr Liu on a couple of occasions, but not since he became party leader.
The Herald on Sunday reported Mr Liu was wanted by authorities in China.
Ian Wishart, editor of Investigate magazine, said last week he had received leaked Internal Affairs documents which raised concerns about Mr Liu's true identity.