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Maurice Williamson, the Minister of Building and Construction, and Prime Minister John Key then opened the first stage of a $70 million construction project launched by the Chinese-born developer after he became a citizen.
The following year, one of his companies made a $22,000 donation to the National Party.
The Department of Internal Affairs (DIA) recommended that the citizenship application of Donghua Liu be declined on the grounds that he did not spend enough time in New Zealand or meet English language criteria.
However, one of Mr Liu's business partners approached Mr Williamson and John Banks - the Mayor of Auckland at the time - and they wrote to the Minister of Internal Affairs, Nathan Guy, asking him to grant citizenship against the official advice.
"Invested in NZ and a lot of support," was a file note for the case released under the Official Information Act.
Mr Guy, who is no longer the Minister of Internal Affairs, told the Herald that he made the final decision on more than 800 citizenship cases and regularly received correspondence from family and supporters of applicants.
He considered all of the evidence and said of Mr Liu's application: "I considered at the time that, on balance, the potential benefits to New Zealand warranted the granting of citizenship."
The official recommendation of whether citizenship should be granted was ignored in 61 of the 1011 cases between 2009 and 2011.
But the 2010 case was one of several that caused concerns among DIA staff, who raised the possibility of favouritism with the Office of the Auditor-General during an inquiry into a citizenship decision made by Labour MP Shane Jones.
Mr Jones was criticised in the report last year but cleared of any corruption over his decision to grant citizenship to a wealthy businessman who had strong links to Labour.
The Auditor-General was also told of other citizenship files involving support from MPs.
An in-depth investigation of those files was beyond the scope of the original inquiry but nothing was found to suggest that decisions were made "as a result of improper influence".
"However, it is clear that the apparent links between different applicants and their agents, or supporters, coupled with strong support from various MPs and subsequent questions from the minister or ministerial officials caused disquiet among some citizenship officers," according to the inquiry report.
The Auditor-General said there was nothing wrong or improper with MPs advocating on behalf of constituents in citizenship cases, or ministers considering those representations.
"However, advocacy of this kind, in particular where the advocate is a fellow MP or known to the minister, clearly presents risks to the integrity of the decision-making system and to the reputations of those involved," the Auditor-General wrote.
No MPs or supporters were named in the report but Mr Williamson and Mr Banks were identified through Official Information Act requests by the Herald.
Mr Williamson and Mr Key opened the first stage of a $70 million property development project in Newmarket in 2011, the refurbishment of the Boulevard Hotel, described as the "brainchild" of Mr Liu.
Both Mr Williamson and Mr Banks declined to comment on their support for Mr Liu's citizenship because it was a "constituency matter".
Others who supported Mr Liu's bid for citizenship were lawyer Jeremy Goodwin and Roy Mottram, who are listed as directors in different companies with him.
Electoral donation records show that Roncon Pacific Hotel Management Holdings Ltd - of which Mr Liu and Mr Goodwin are directors - made a $22,000 donation to the National Party in 2012.
Mr Mottram confirmed he approached Mr Williamson and Mr Banks to support Mr Liu's citizenship bid as he was making a very significant contribution as a businessman in Auckland, particularly in the construction industry.
"John's support was just a matter of course because the activity was in Auckland City, he was the mayor and he was supportive of things that were good for Auckland," said Mr Mottram.
"Obviously, if you're the Minister of Building and Construction, you would want to promote building and construction, which we have been involved with for a long time."
Mr Mottram said the requirements for New Zealand citizenship, which include the amount of time spent in the country and language requirements, were out of date.
"A lot of active, global businessmen are never in one place for any length of time ... People who have global businesses are global citizens."
How it unfolded
2010: Businessman Donghua Liu granted NZ citizenship by Nathan Guy, the then Minister of Internal Affairs, against official advice after being lobbied by Maurice Williamson, Minister of Building and Construction, and John Banks, the Auckland Mayor at the time.
2011: Mr Williamson and Prime Minister John Key attend the opening of the first stage of Mr Liu's $70 million redevelopment in Newmarket, Auckland
2012: Roncon Pacific Hotel Management Holdings Ltd - of which Mr Liu is a director - makes a $22,000 donation to the National Party.
- Jared Savage of the NZ Herald