Conservatives leader Colin Craig says he is taking action to shut down a satirical website.
The Electoral Commission admits the website is escaping scrutiny because its owners are anonymous.
The colincraig.co.nz site uses images of Craig and Conservative Party slogans such as "vote for something".
Although the website includes disclaimers that it is satire, it has no promoter statement and mocks the party as being made up of "businessmen that show women where to go", which will bring fresh thinking to Wellington.
"Our role will be to give the Government a backbone; to give them the support they need to make the tough calls, whether they're right or wrong, unless the public say otherwise, in which case we won't be the Government's backbone, we'll do what the mob wants."
Under the Electoral Act, anything which could "reasonably be regarded as encouraging or persuading voters" to either vote or not vote for any candidate or party is regarded as an election advertisement.
However, the colincraig.co.nz site appears to have used an offshore shell company to hide its ownership.
A spokeswoman for the commission said that might put it beyond its scrutiny.
"Where the identity of the person responsible for publishing an election-related webpage is unknown, the commission is not in a position to determine whether the exemption for non-commercial expressions of personal political opinions applies or to take the matter further," she said.
Craig said today the situation was "frustrating", but he had taken steps to challenge the domain name.
His advice was that the website had a week to respond, he said.
"They either have to acknowledge who they are and put forward their case as to why they should get to keep it" or it would be shut down, Craig said.
"Our view is that they actually have breached the law, so I don't think they are going to suddenly turn up, put their hand up and say, 'oh, yes, that was me'."
Voters could be confused by the site, especially once it had been reported on by other websites and news organisations, he said.
Craig has previously threatened the satirical Civilian website with defamation, which he said today had resulted from secondary reporting of its content.
He hinted today that if the owners of colincraig.co.nz did come forward, they too could face legal action.
If those behind the site admitted to owning the website "they are going to be very likely the in breach of the Electoral Act for a start, and they may well be liable, depending on how it's taken and how it's presented, but they may be liable for other things as well."
Voters could be influenced by the website, he said.
"My concern is whether anyone gets influenced by this, takes any of it for real. My experience is not everybody knows their way around the internet well enough to know what's spoof and what isn't."
"It may well influence some uninformed voters ... Not everyone pays a lot of attention. They go off small details sometimes. If they don't know me and they haven't read anything else or know anything to the contrary, they might think it's for real."
Although the colincraig.co.nz website is responding to emails, it is refusing to say who is behind it.
"Our policy is quite explicit that we don't like people behind people, unless they're married," it said in response to questions from Fairfax Media.
The colincraig.co.nz website appears to be down presently, but can still be viewed here.