Opposition parties have accused the Government of engaging in electioneering ahead of the local and European elections.
Cabinet approved the National Broadband Plan on Tuesday.
The sole remaining bidder in the tender process was announced as the preferred bidder for the 3 billion euro roll-out of broadband to 540,000 homes and businesses across the country.
Fianna Fail communications spokesman Timmy Dooley said: "This announcement has all the hallmarks of an election stunt and I think people will treat it with an air of scepticism."
He also said the plan would deliver broadband to a third less homes, take three times longer to do so, and cost six times the original price.
"On top of that, the state will not own the network built and paid for by the taxpayer," he added.
Mr Dooley accused the Fine Gael-led Government of completely mismanaging the project from the beginning and wasting taxpayers' money.
Government signs off on €3 billion National Broadband Plan
"I think it's very clear that this process is flawed," he said.
"The reality is that when there is just one bidder at the table you have to accept their terms and conditions."
Labour Party leader Brendan Howlin claimed Fine Gael was putting electoral politics ahead of the public good.
Mr Howlin said: "Labour wants to see rural broadband delivered, but this plan risks leaving people in rural Ireland totally dependent on a private monopoly, which will ultimately be able to charge what it wants for access to the internet.
"The timing of this announcement is purely to influence the upcoming local and European elections. A contract hasn't even been signed yet and the Government is simply announcing a preferred bidder in a situation where there only is one bidder.
"Fine Gael's plan not only flies in the face of official advice that it is poor value for money, but it simply doesn't make sense," he added.
'We have to drive six miles to go online' - rural Irish family furious at poor internet coverage
People Before Profit TD Brid Smith said the decision was motivated more by election concerns and not with delivering broadband to rural communities.
She described the tendering process as a "historic fiasco" that would make the National Children's Hospital "look like a bargain".
"It is beyond belief that even after spending 3 billion euro on this, the State will not own the finished infrastructure after 25 years," she said.
She called on Government to take full ownership control of whole project.
"This farce needs to stop and the state needs to take control and ownership of providing broadband by using existing semi-state companies like the ESB to provide it," she added.
Bringing high-speed broadband to rural Ireland will cost at least €3billion, Taoiseach confirms
