Chorus chief executive Mark Ratcliffe said it meant the company "simply will not be able to borrow the sums of money we need to make up to a $3 billion investment in UFB".
The company's share price fell 6.84 per cent yesterday and another 5.5 per cent today, closing at $2.315.
Rating agencies Standard & Poor's and Moody's said today they are both reviewing the company's credit rating following the regulator's cut.
Prime Minister John Key said yesterday the Government was considering how it would respond to the situation but would not rule out legislating over the top of the Commerce Commission's decision, lending money to Chorus or even taking an equity stake in the company.
Key told Parliament today that Communications Amy Adams was likely to indicate tomorrow how the Government would "try and understand" the commission's ruling and "what other possible alternatives and options [are] available".
Asked by the Herald this afternoon if the Government would be announcing what options it would be taking up or not, Adams replied:
"We're going to be announcing how we sort of see this playing out from here and what our next steps are."
Adams said the Government was making sure it had good information on the impact of the regulator's decision and on what it needed to consider.
She said the Government already has non-voting preference shares in Chorus and that it would continue to hold this stake.
"But no-one's looking to nationalise this company, that's not something that's front of mind for us," she said.
Labour's associate Communications and IT spokesperson Clare Curran said the "only responsible position" for the Government was to uphold the regulator's decision.
"Any bail-out, equity stake or loan will be corporate welfare," she said today.
"The Government's behaviour over Chorus has been bizarre. They appear to be against any move to provide Kiwi households with lower prices," she said.
Forsyth Barr senior equity analyst Blair Galpin said he didn't expect a final decision on what the Government would do by the end of the year.
"You would expect they would take a bit of time to come to any sort of final decision," Galpin said.
"But they could give a signal before that," he said.
- additional reporting: Adam Bennett