The National Broadband Plan could cost in the region of €3 billion, the Oireachtas Committee on Finance has heard.

The claims were made by Sinn Féin deputy leader Pearse Doherty during tetchy exchanges with Taoiseach Leo Varadkar, who said there has been a "spectacular overrun and underestimation" of the project costs.

Mr Varadkar was before the committee this afternoon where he faced questions about spending in his department.

Fianna Fáil TD Barry Cowen said that €22 million has been spent to date on the controversial plan and "not an inch of fibre optic cable in the ground yet."

Yesterday, the Taoiseach told the Dáil the NBP 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.

Responding to Mr Cowen today, the Taoiseach said: "We have one bidder left, yet to be designated as the preferred bidder. We have yet to make a decision as to whether we go ahead with the national broadband programme. The cost is going to be multiples of what has been projected."

"Going ahead with it would not have a significant impact on this year, but it would have an impact on future years. We will have to bear that in mind in making any decision."

The Taoiseach said the project was very different to the national children's hospital, saying "It is a 30-year project so the cost is spread over 30 years. It involves private finance and user fees so it’s a very different financial model."

He said that he intends to consult with Opposition parties before any contracts are signed as it is a 30-year project that will extend beyond the life of this Dáil and the life of the Government.

Read more: Is rural Ireland any closer to getting high-speed broadband?

Pressing the Taoiseach about the cost of the plan, Mr Doherty said: "There was a cost benefit analysis already done on this project at the early stages, based on a cost of €500m. This could end up in the region of €3bn.

"This is a spectacular underestimation or an overrun on a planned project of national importance. And it really, really questions how Government are handling major capital infrastructure projects," he said.

The Taoiseach said: "There is no overrun here. This project has not even started. A tender has come in  and it’s a certain price and it is our decision now as a Government and as an Oireachtas whether we want to pay that price, whether we believe it is worth it or not. There is no overrun here."