Prime Minister John Key says Pansy Wong has more questions to answer about possible misuse of her ministerial position on a private trip to China, but she is not his responsibility because she is no longer a minister.
Labour Party MP Pete Hodgson says a Chinese local government website shows Mrs Wong, identified as a minister, promoting her husband's investment in a hovercraft company.
Mr Key says he has not seen the website, but it does raise more concerns. However, he says he cannot sack her as an MP.
Her future as an MP is up to her and Parliament's Speaker, Lockwood Smith.
Labour says the former minister of women's affairs used her ministerial position to further her husband's business interests while on a private trip to China subsidised by taxpayers.
Labour leader Phil Goff has again called on Mrs Wong to resign from Parliament over the matter.
She resigned as a Cabinet minister on Friday after questions were asked about her husband Sammy Wong doing business while on the trip.
The MP for Botany faces a Parliamentary Services inquiry over the matter and has not made any public comment since she resigned her portfolios.
Mrs Wong is not answering her phone and refuses to talk about her links to her husband's business ventures.
Mr Goff says it is not good enough that the MP is refusing to talk and she should resign from Parliament.
Mr Goff says he made former Labour MP Chris Carter front up about travel expenses but Prime Minister John Key is continuing to protect Mrs Wong.
"She knows what she's done - she must be held accountable for that. She is a parliamentarian, she was a minister, she must front up an justify herself."
Earlier on Tuesday, Mr Key said he stood by his advice to Mrs Wong not to talk until a Parliamentary Service investigation into her use of subsidised international travel had been completed.
"MPs need to be able to answer questions honestly, truthfully and, hopefully, directly. And that's not possible when they don't have all the facts."
Mr Key says those facts are being gathered by Parliamentary Services and he expects her to front when the report is issued.
Though the affair is damaging to the Government, Mr Key says neither he nor his office has spoken to Mrs Wong since last Friday.
Wong companies registered at electorate address
There are also questions about why two companies associated with Mr Wong are registered at his wife's electorate office address.
Company records show Sampan Enterprise Limited, of which Sammy Wong is the sole director and shareholder, is registered at the office address, as is Shipley and Wong Limited, whose shareholders are Mr Wong and Dame Jenny Shipley, a former prime minister.