Auckland Council has told activist Penny Bright to pay $29,000 owed in rates within 10 days or risk losing her Kingsland home.
A court-conducted sale could be the end of a six-year rates strike for Ms Bright and cost her the half a million-dollar cottage, which she says she bought in 1990 for $144,500 when she was a welder-tutor and repaid the loan in only nine years.
But the self-styled "private ombudsman" has vowed to fight on.
In a letter to her, the council credit control team said it had district court judgments against her for the unpaid rates, plus legal costs and interest.
The council intended to enforce the rulings by having the house sold.
Ms Bright, who has twice contested the mayoralty election and won 12,000 votes last year, said she would not pay until she knew rates money was being spent properly.
"It is Auckland Council that is breaking the law by not upholding its statutory duties ... for open, transparent and democratically accountable local government and by not providing the devilish detail of where exactly rates monies are being spent on private sector consultants and contractors."
She said the letter came after she complained four times to police about the council.
The complaints included Mayor Len Brown not disclosing hotel stays, particularly at SkyCity, and her physical removal from a meeting of the council chief executive review committee after being denied speaking rights.
"So, as a New Zealand anti-corruption whistleblower, I have been censored, assaulted and now Auckland Council has threatened to sell my house to enforce disputed rates payments."
Council spokesman Glyn Walters said a rating sale notice was issued as a last resort after the legal process and repeated reminders and all collection methods had failed.
The court - not the council - conducted the sale six months after the court served notice of sale. Any proceeds left after cost recovery was returned to the property owner.
Mr Walters said the council developed a policy in pursuing rating sales last March and undertook a review of rates arrears in October.
One hundred and seventy-nine ratepayers were being reviewed and about $2.5 million was outstanding in rates.
"Very few of these will result in actual sale of property as many ratepayers settle the arrears during the rating sale process."
But Ms Bright said she did not have cash to settle the rates bill, which was $2197 last year, based on the capital value of $530,000. Her only income was a flatmate's contribution.
"I've been working full-time in the public interest since 2000."
Penny Bright's rates
$530,000 capital value on home for rating purposes.
$22,242 rates and penalties overdue June 30, 2013.
$6866 legal costs and interest.