The Taoiseach has compared opposition leader Micheál Martin to a parish priest "who preaches from the altar, telling us to avoid sin while secretly going behind the altar and engaging in any amount of sin himself".

The pointed attack came in the Dáil this afternoon during questions to Leo Varadkar, as the Fianna Fáil leader asked about the National Development Plan (NDP).

The Taoiseach said he is always "amused and bemused" that Mr Martin accuses him of being "partisan and personal" when he does just that himself.

Mr Martin reminded the Taoiseach that at the core of the NDP was a promise from the Government that everything was costed and there would be full transparency.

He claimed that real time information about the progress and costs of various projects is being withheld. 

"There is now a irreconcilable gap between the reality on the ground and what is being claimed," the Fianna Fáil leader said.

He pointed out that the children's hospital is now "well on its way to hitting the €2bn mark, which the Taoiseach said was a conspiracy theory, and the broadband plan tracking to a €3bn figure, which was also dismissed until it was exposed".

Mr Martin said there is a need for honesty with the public about the cost of the NDP.

He asked the Taoiseach for clarity on a number of projects such as the upgrade of the Dunkettle Interchange outside Cork city, and for a commitment to update the detailed tables of costs on projects under the NDP for the next four years.

During the exchange about the delivery of capital projects, Mr Martin said: "There is a need for honesty with the public in terms of the impact of the billions of euro in overspend on the Government's plans and projects. 

"Earlier, I asked the Taoiseach about the Dunkettle Interchange. I appeal to him not to be petty, silly and idiotic in terms of his response by asking whether I am for or against the Dunkettle Interchange.

"The procurement process is completed. This project was meant to be up and running in early 2018, in terms of construction, with works to run from 2018 to 2022. The indicative cost for this project of €100 million has increased to €115 million," Mr Martin added.

Responding Mr Varadkar said: "I am always amused and bemused that Deputy Martin likes to accuse me of being partisan and personal, yet as is evidenced by his name calling today, he is very capable of being partisan and personal himself.

"He kind of reminds me of one of those parish priests who preaches from the altar, telling us to avoid sin while secretly going behind the altar and engaging in any amount of sin himself."

Responding to the Taoiseach's comments, Mr Martin tweeted: "I think this reflects more on the Taoiseach than anyone else."