Opposition parties are convinced the Government is going to sell KiwiRail despite ministerial denials.
It announced on Wednesday KiwiRail's network and ferry assets will be written down from $13.4 billion to $6.7b and put into a new state-owned enterprise.
Finance Minister Bill English says it's "just part of a clean up" designed to turn KiwiRail into a viable business.
"I think everyone agrees this company was not worth $13b," he said.
The move will leave the commercial arm of KiwiRail carrying assets of just over $1.1b.
Labour says the Government is setting it up to fail.
"KiwiRail is being lined up as the next asset to go on the auction block, just 24 hours after a law was passed allowing it to sell off our power companies," state-owned enterprises spokesman Clayton Cosgrove said.
"It has no intention of turning the company around, it is simply softening up New Zealand for the news that KiwiRail is part of the asset sales agenda."
NZ First leader Winston Peters says KiwiRail is being deliberately devalued so it can be "flicked off cheap" to a private investor.
"Given our disastrous history of rail infrastructure when it was sold to private owners by National in the 1990s, this latest threat needs to be taken seriously," he said.
"The rail network is a critical part of our transport infrastructure, not a financial bauble to be parcelled around to National's financial friends."
Mr English says that isn't the Government's intention.
"We are not trying to sell KiwiRail," he told reporters.
"The commercial value of it would be pretty low."
The railways was privatised in 1993 and bought back by the last Labour government for $665 million in 2008, when it was re-named KiwiRail.
NZN