The country's most senior civil servant in charge of public spending has agreed to appear before the Oireachtas Finance Committee to answer questions on the cost overrun at the National Children's Hospital.

But Robert Watt - the Secretary General at the Department of Public Expenditure and Reform - suggested he would only do so as an alternative to appearing before the Public Accounts Committee (PAC).

In a letter to the committee chairman John McGuinness, seen by RTÉ News, Mr Watt said he would be happy to do so if "it is the most appropriate committee". He asked Mr McGuinness to confirm with the chair of the PAC which one is the most important one for him to appear before.

Following a three-week row over whether he should attend or not, Sinn Fein's Pearse Doherty wrote to committee members last night proposing it should not accommodate Government business - including its meeting this morning with the Finance Minister - until Mr Watt agreed to attend.

Mr Doherty was supported in this proposal by the Committee Chairman, Fianna Fail's John McGuinness. At the meeting this morning, Finance Minister Paschal Donohoe agreed to intervene in a row if the committee facilitated the estimates process, which he said involved important spending in areas that he said were important in the context of Brexit - including the Revenue Commissioners, The Office of Government Procurement and the Secret Service.

A row followed in the committee over whether they should continue to meet with Mr Donohoe to discuss revised estimates.

Mr Doherty said the work of the committee is a "two-way street" and the work of Government should not be facilitated if the Government, in turn, refuses to answer questions.

"We are either a serious committee or we are not," he said. "The only other people who have refused to come before us are the vulture funds and we have lambasted the fact that they have refused to come before us.  We have our own General Secretary who is refusing to come before this committee."

Fine Gael TD John Deasy said the accusation that Mr Watt had refused to appear before the committee should be withdrawn, given that he had indicated his willingness in last night’s correspondence.

The Waterford TD accused Mr McGuinness and Mr Doherty of playing games.

"You are bringing this to a head for political reasons, that’s really what the game is here. I’m around long enough to see that a ready-up is being orchestrated with regards to the estimates and the minister coming in here this morning."

Minister Donohoe said that a refusal to facilitate the estimates process "does send out a particularly troubling signal of how we can conduct our business."

Meanwhile, the Public Accounts Committee is to ask the National Paediatric Hospital Development Board to reappear before them.

Sinn Féin TD David Cullinane said the committee had a "false meeting" when they appeared before them earlier this month, because members did not have minutes of board meetings and the Mazars report into the cost overruns.

"We are now armed with the information," Mr Cullinane said, adding that the committee should not accept "being kept in the dark".

He also asked that both Robert Watt and the civil servant appointed to the board, the government's Chief Procurement Officer, appear before them.

Mr Watt is scheduled to appear before the PAC on 7 March.

Labour TD Alan Kelly said there was a wider issue to be examined around processes on all other projects.

Additional reporting: Edel McAllister