Chorus shares struggled at just $1.95 at midday, after Communications Minister Amy Adams announced plans for an independent appraisal of the company's books.
Chorus has rolled out ultra-fast broadband cable in parts of Dunedin and around New Zealand.
Stock had fallen as much as 12% to $1.85 - the lowest point since the company listed on the NZX in 2011.
The Government decided to probe Chorus' finances before making a call on intervening in broadband prices.
That followed a Commerce Commission decision on Tuesday to make a 23% cut to what Chorus charges internet retailers for broadband services and line access over its copper network.