A trust that funded Auckland Mayor Len Brown's election campaign and kept donors' identities secret is under police investigation.

Auckland police confirmed yesterday that they have been investigating the New Auckland Council Trust - that donated more than $770,000 to Browns' 2010 and 2013 campaigns - since February.

The investigation would determine if the trust breached the Local Electoral Act by keeping donors' identities secret, media reported.

It was sparked by a complaint from former police prosecutor and unsuccessful 2013 Albert-Eden-Roskill ward candidate Grace Haden.


Ms Haden, a private investigator and anti-corruption campaigner, told the Herald she looked into the trust after seeing its donations of $499,000 in 2010 and $273,375 last year on Brown's electoral return.

Her concerns centred on no person being named as contributor on an electoral return, as required under changes to the act introduced before last year's local government elections.

Mr Brown's return names the trust, but Ms Haden said trustees should have been named and she complained to the Electoral Commission in November, who took the issue to police in February.

Auckland Detective Inspector Chris Cahill said: "An investigation was initiated and is ongoing."

It was reported yesterday that Greg Presland - the main trustee of another entity that paid almost $20,000 in anonymous donations to former Labour leader David Cunliffe during Labour's leadership contest last year - was involved in this trust, too.

Mr Presland, who sits on the Waitakere Ranges Local Board, would not comment last night.

A statement from Mr Brown's office said his campaign complied with legislation and the trust structure was a common practice before the rule change.

"The New Auckland Council Trust made its final donation before the law changed."