The Government has been hammered for leading the public "down the garden path" in signing the National Broadband Plan.
The project has been dubbed a "bad deal" for the taxpayer by the Labour party which said it shows that Leo Varadkar's Government has "no regard for public money".
Fianna Fáil described the €3bn plan to roll-out broadband across the country as "an absolute shambles" but has expressed doubt as to whether the contract can be changed now that it has been signed.
However, Social Democrat co-leader Catherine Murphy said she believes that the contract could and should be revisited.
After significant delays and controversy, the Cabinet signed off on the plan to roll-out high-speed broadband to the 1.1 million people living and working in the nearly 540,000 premises including 100,000 businesses and farms, and over 600 schools, where commercial operators will not commit to delivering the service.
Fianna Fáil's Stephen Donnelly said the contract "does not represent value for money" and said it had come at the end of "a completely failed and shambolic, so-called competitive, tender process".
He said: "We have watched with bemusement and horror the growth in the cost of this. We were promised this, I think, back in 2012 and we were told that it would cost €315 million.
"Then we were told it would take a few years longer and it would cost €500 million. Then we were told it would take a few years longer but it will be €3 billion."
He said the public was being "led down the garden path" and said it was "no coincidence" that the contract had finally been signed ahead of this month's by-elections.
Labour leader Brendan Howlin said it was wrong of the Government to sign the contract.
"It just echoes again the spendthrift nature of the government. They have no regard for public money after the decade of difficulties the Irish people have gone through so they can throw money at broadband or they can throw money at the National Children's Hospital, or at the Metro without having any regard for value for money."