The slump in the share price of line network owner Chorus has been put down to misinterpretation and miscommunication of a Commerce Commission decision released last week.
Investors understood there had been a change, but not what the change was, a broker said.
There was a feeling of "here we go again" with more regulation for the company driving down the share price.
Chorus, which was structurally separated from Telecom to be part of the Government's ultra-fast broadband project, opened on Thursday last week at $3.57 a share.
But after the commission released a draft ruling on the pricing for competitors to use its copper line network, the shares fell to $3.25. The next day, they were down to $3.04, a fall of 43c in two days.