The Securities Commission says unsolicited share offers could soon be more tightly regulated.
Entities registered by Christchurch man Bernard Whimp have sent out a mass mail-out to shareholders over Christmas offering to buy their shares in major companies.
The offers were made by a series of limited partnership and valued the shares at about two thirds what they would fetch if sold by a broker.
The partnerships, include Carlyle Securities, Pearson Securities and Fairfield Securities.
Mr Whimp was banned as a company director for four years in October 2006.
The commission's director of investigations and litigation, Sue Brown, says aspects of the offers should raise a red flag and investors should check current stock prices before selling.
Ms Brown says she is in discussions about changes to the Securities Act that would tighten the rules on such offers.
That could involve making it harder for people to access the share register, as well as the introduction of new rules requiring such offers to include the present market value of the shares, she says.
The president of Greypower, Roy Reid, says the share purchase offers are misleading and place too low a value on the shares.
Mr Reid says he believes such schemes should be illegal, but until they are, it is a case of let the seller beware.