"Port of Tauranga does not believe the proposed offer is illegal, however we view it as being unethical," he wrote.
Pyes Pa resident Colin Bidois, whose small shareholding in the port meant he could be targeted, was dismayed by the cheek of the company.
"It is insulting. Do they think that we are so close to the South Pole that all our brains are frozen?"
Mr Bidois said the unsolicited offers were in his opinion "preying on vulnerable shareholders" and it was quite likely that some could be naive enough to succumb to the big dollars, seeing it as a bit of quick money.
TrustPower chief financial officer Robert Farron said 12 shareholders accepted the unsolicited offers made by Bernard Whimp, the earlier "poster boy" of the practice whose activities led to a tightening of the rules so that offers now had to be accompanied by a statement of the actual market value of the shares or bonds.
Mr Farron was pleased to report that only one shareholder had sold to Washington Securities in the May offer and he was fairly confident that the more sophisticated approach to investing by bond holders would see none of them take the bait.
Washington Securities offered just over $5 per TrustPower share, at least $2 below what they were worth on the sharemarket.
The latest bond offer was 80c per bond compared with its market price of nearly $1.06.
Mr Farron said a lot of the company's 13,500 shareholders were elderly people, some of whom would have had the shares sitting in the bottom drawer since they were issued in 1994. He said some of New Zealand's top 10 listed companies had been targeted on an almost rotational basis over the last 12 months.
If the latest shareholder to succumb had held the standard issue of 2000 shares, they would have been out of pocket by nearly $4000.
A sharebroker would have taken a commission of one or two per cent of the market value of the shares.
Mr Farron said the company was targeting people who could fall for the offer in the letter's headline, without reading the market value of the shares further down. Other companies warning shareholders included Heartland New Zealand, Tower, Fletcher Building and Vector.
The lure of Tauranga's big companies
Port of Tauranga
134 million shares held by 9500 shareholders.
Valued at just under $2 billion.
90 per cent of shares held by 10 per cent of investors.
TrustPower
315 million shares held by 13,500 shareholders.
Valued at $2.25 billion.
Nearly 84 per cent held by Infratil and TECT.