The new Financial Markets Authority is threatening to take tougher action against Bernard Whimp, a notorious and persistent stock buyer.
Mr Whimp has made a number of ''low ball'' offers to buy shares in listed companies at prices substantially below what they trade at on the market.
On the FMA's first day, chief executive Sean Hughes said the agency is considering forcing Mr Whimp to include a warning notice about his activities in any future offers he makes.
He warns investors to treat any offer from Mr Whimp with caution and points out they would get more selling their shares through a sharebroker.
Mr Whimp has three days to make submissions.
The FMA will make its decision at the end of the week.