Labour leader David Shearer says he will stand MP Shane Jones down if there is an investigation by a body such as the police or Auditor-General into Mr Jones' decision to grant citizenship to a Chinese businessman.
Mr Jones yesterday broke his silence on his 2008 decision to give citizenshipto William Yan - also known as Yang Liu and Yong Ming Yan - saying he granted the citizenship on "humanitarian grounds".
Mr Jones initially would not reveal what those grounds were, but later told 3News a Department of Internal Affairs official had told him Yan would be executed and have his organs harvested if he was returned to China. Mr Jones said he was given the impression it would be a death sentence if he declined the citizenship - and he had a file note of that conversation.
He had done so despite officials' advice Yan did not meet the character requirements for citizenship because of questions about his multiple identities and an Interpol red notice on him because he was wanted for arrest in China.
Mr Jones spoke out after Yan's trial on charges of making false declarations on immigration documents wound up this week. Yan has pleaded not guilty to those charges and the court has reserved judgment until tomorrow.
Pressure is mounting for an inquiry into the decision.
Asked if it seemed a bit murky, Prime Minister John Key said "it feels a bit like that". He said he was willing to take Mr Jones at his word, but believed he still had questions to answer.
"The law allows a minister to say yes or no. That isn't the issue. The issue is why he said yes when the officials told him to say no," said Mr Key.
Mr Shearer yesterday said he would stand down Mr Jones if the police or the Auditor-General investigated him.
The Office of the Auditor-General said it had not yet received any request for an investigation into the issue. It can mount its own investigation if it considers it to be in the public interest.
Mr Jones said he was not concerned by Prime Minister John Key's criticism.
"I can understand Prime Minister Key wanting to see someone like myself stood down. It's the politics of utu. We have a crack at John Banks, they have a crack at Shane Jones."
He was relaxed about the trial and would make a more detailed explanation after its conclusion.