The Labour Party has accused Fine Gael of making the National Broadband Plan a political project that does not make financial sense.
Finance Minister Pascal Donohoe went against advice from officials in the Department of Public Expenditure that the plan was a massive risk to state finances and a leap of faith by the Government.
Officials also warned some projects may have to be cancelled to meet the €3bn cost of the plan.
Documents published on Wednesday showed that public spending officials said it represents an "unprecedented risk" to the State.
The correspondence showed the Department of Public Expenditure strongly warned against appointing the preferred bidder for the project.
Officials were significantly concerned about cost and affordability.
The documents also showed that Robert Watt, secretary-general of the Department of Public Expenditure, expressed his concerns in a letter to Mark Griffin, his counterpart in the Department of Communications.
The letter warned committing to the plan would be a major "leap of faith" by the Government.
Mr Watt highlighted the "unprecedented risk that the State is being asked to bear in the event that the current NBP contract is recommended for approval by Government".
Labour leader Brendan Howlin has said the Government looks set to repeat mistakes of the past.
"It's obviously now a political project, rather than one that is based on sound financial judgement.
"We set up a Department of Public Expenditure to ensure that we wouldn't revisit the mistakes of the past - that seems what we're going to do, with a Government now that looks at short-term political gain over all else."
"Every party in the Dáil wants to see a high-speed rural broadband delivered as soon as possible, but this mechanism is obviously not the way to do it".
Mr Howlin also said it is unacceptable for so much money to be invested by the State, without having full ownership.
"The notion that you would hand over the network to a private entity is what really sticks in the throat of most people.
"If the State is going to invest in that level of taxpayer's money, then we need to own the infrastructure at the end of it - and that's the fundamental point I am making".