The Taoiseach has told the Dáil the National Broadband Plan will cost "many multiples" of the original estimate, and the Government would have to decide whether the public finances can bear the cost.
He said he hoped to make a decision on whether the plan was to proceed, before Easter.
Leo Varadkar was responding to the Fianna Fáil leader, Micheál Martin, who said the tendering process has been a "nightmare" and "torturously slow".
Mr Martin asked whether there was now a question mark over whether the plan would be rolled out at all.
Speaking during Leaders' Questions in the Dáil, the Taoiseach said that while enormous progress had been made on the delivery of high-speed broadband, there are still 500,000 homes and premises that do not have access to it.
He said there is still one remaining bidder in the National Broadband Plan, and that bidder has not yet been designated by the Government as the preferred bidder.
Mr Varadkar said the government had received the tender and it is "many multiples of the original cost estimate".
"We have not taken the decision to designate the remaining bidder as the preferred bidder, nor have we signed any contracts on the project. That is a decision that has yet to be made," he said.
"It is a decision that cannot be made at this stage because due diligence is still being done. There is an international review panel doing a cost benefit analysis, assessing whether the project makes sense from the cost point of view."
He added: "Because it is going to be much more expensive than the original estimate, we have to see how the public finances can bear it" and, referring to Brexit, he added "obviously the events of the next couple of weeks will tell a story in that regard".
Mr Martin asked when the Dáil could expect some precision around the potential costs of the Enet submission, and when a decision could be expected on whether the plan would progress.
Mr Varadkar said his "objective is to be in a position to make a decision before Easter of this year."
"Due diligence is still under way, and because the cost will be many multiples of what was envisaged it will have an impact on the public finances, and the events of the next couple of weeks will help us to decide whether we can bear that impact on the public finances," the Taoiseach added.
"The impact on 2019 would be miniscule, but there would be a significant impact on 2020, 2021 and onwards."
He said the project would have an impact not just on this Government, but on future governments.
"That's why we want to be transparent and consult the Oireachtas on it," he said.