Auckland mayor Phil Goff's election expenses have been referred to the SFO.

The Serious Fraud Office has received a referral from police in relation to Auckland Mayor Phil Goff's election expenses.

The SFO said it would be assessing the matter and had no further comment at this time.

Electoral law dictates candidates can accept anonymous donations under $1500, but must disclose the names of donors who contribute more than that sum.

A spokeswoman for the mayor said he had "no knowledge of a complaint being referred to the SFO nor of any irregularities".

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"We will not be making any further comment until we have been contacted," she added.

Auckland Council has been contacted for comment.

Earlier on Friday, the SFO announced Christchurch mayor Lianne Dalziel had also been referred to the SFO.

In September, Auckland's electoral officer, Dale Ofsoske, passed on to police a complaint about Auckland mayor Phil Goff's 2016 election expense declaration.

Goff's $366,000 fundraising auction declaration did not specify individual donations or purchases, which included the sale at an auction of a book for $150,000. The book had belonged to Goff, a former minister of foreign affairs, and had been signed by Chinese President Xi Jinping.

Police made "a number of inquiries" before the timeframe for any prosecution expired in December, rendering them unable to progress the matter.

Ofsoske told Stuff at the time the complaint was under section 112D of the Local Electoral Act 2001, 'Filing a false return of electoral donations and expenses'.

In 2009, then-Waimakariri deputy mayor Dan Gordon was discharged without conviction after a 2009 court case for electoral fraud. He listed a $5000 donation as anonymous then later named the benefactor.

The recent complaints come a week after the SFO announced it would investigate the New Zealand First Foundation over concerns about donations and an apparent slush fund of half a million dollars.