Progressive leader Jim Anderton has launched an extraordinary attack on the Electoral Commission for referring him to police for a possible breach of the Electoral Act.
The referral follows a complaint, brought by right-wing blogger WhaleOil, about a letter the Wigram MP sent to voters endorsing the Labour candidate Megan Woods in November's election.
If found guilty, Mr Anderton could face a fine of up to $40,000.
But Mr Anderton, who was referred to police over election advertising before the 2008 election, said he had done nothing wrong.
"Nonsense, rubbish, waste of time, waste of police resources, waste of space. It's just as ridiculous as the referral I had to police at the last election. They threw it in the bin then and they'll do it again now.
"I'm authorised to send my constituents any message I damn well like. This is my electorate.
"And if the Commission wants to start stopping electorate MPs from communicating with their electorate, they'd better get prepared for a breach of privilege complaint, because that's what it amounts to.
They are interfering with the regular work of an MP."
He said he would co-operate with police and respected the right of the commission to refer him.
"But they were wrong to do it last time, and are equally wrong this time ... Last time police were furious with the rubbish they had to deal with from the Electoral Commission.
"They have a few things like rape and pillage going on around the country, and this is simply ridiculous to tie up senior members of the police force with this kind of garbage."
Mr Anderton said the letter was sent outside the regulated period under the Electoral Act, but the commission referred it to police on the basis that the letter was not properly authorised.
All election advertising, regardless of when it is published, must contain a promoter statement.
The letter was authorised by Mr Anderton but, under the law, a person only can be a promoter if they are a party secretary, candidate, registered promoter or unregistered promoter.
A person cannot be an unregistered promoter if they are involved in the administration of the affairs of a political party.
In a letter sent to WhaleOil and published on the blog, chief electoral officer Robert Peden said: "It is the commission's view that the publication of the letter constitutes a breach of section 204B of the Electoral Act because Mr Anderton is involved in the administration of the affairs of the Progressive Party and is therefore not entitled to promote an election advertisement."
Megan Woods, Dunedin North National candidate Michael Woodhouse and Labour's Charles Chauvel have also been referred to police for possibly breaching the law.By Derek Cheng Email Derek