It has emerged that a second member of Fianna Fáil's frontbench voted last week for a colleague who was not in the Dáil chamber.

The party's Brexit spokesperson Lisa Chambers has confirmed an Irish Times story that she mistakenly voted for the party deputy leader Dara Calleary last Thursday.

In a statement, Ms Chambers said she "inadvertently" sat in Mr Calleary's seat, which is next to her seat, and "pressed the button once in error" when he was doing a radio interview.

She said that "no one asked" her to cast that vote and, when she realised, she "immediately moved to my own seat".

The incident happened during the same period that Fianna Fáil's Niall Collins voted six times on behalf his colleague Timmy Dooley, who was not in the chamber.

In a statement, Mr Calleary said: "I did not, and would not, ask any other deputy to vote for me in the Dáil."

He added that Ms Chambers "mistakenly did not correct the record on the day, hence my name is registered".

Mr Calleary also said that Ms Chambers had "contacted the Ceann Comhairle this evening to advise him of this".

When asked why she told RTÉ's This Week programme earlier on that she had never voted for a colleague, Ms Chambers said: "Honestly, I took the question as an intentional vote for someone else."

She added: "What happened was a genuine mistake. I believed that this error was insignificant when asked on RTÉ today ... For this I apologise."

Listen to Lisa Chambers on RTÉ's This Week here:

It comes after the Fianna Fáil leader Micheál Martin asked Mr Dooley and Mr Collins to stand down temporarily from the frontbench over the Dáil votes controversy.

Mr Martin told journalists at the party's Bodenstown commemoration that he spoke to both men and they accepted his decision.

He said he did not think what happened was "acceptable".

Mr Martin said that both TDs assured him that they would cooperate fully with Ceann Comhairle Seán Ó Fearghaíl in relation to the incident.

Earlier, Mr Calleary described as "unusual" an admission by his party colleague Mr Dooley that he was absent from the Dáil chamber when his vote was recorded.

Mr Ó Fearghaíl has ordered a report into the matter after Mr Dooley left the Dáil last Thursday to take a phone call, and his colleague, Mr Collins, voted for him six times.

Speaking on RTÉ's Morning Ireland, Mr Calleary said: "The integrity of the voting system within the Oireachtas, and within the Dáil, is hugely important."

He said he welcomed the examination announced by the Ceann Comhairle, saying he had "complete faith" in Mr Ó Fearghaíl's ability.

Mr Calleary said he would support "whatever decision" the Ceann Comhairle opts to take following the completion of the report, including an investigation by the Dáil Committee on Procedure and Privileges.

Asked if the relevant Dáil votes should be re-run, Mr Calleary replied: "I don't see why not ... We have a Business Committee, which assesses business, and it would be a matter for them."

Speaking to RTÉ News in Dublin, Taoiseach Leo Varadkar said the Ceann Comhairle was investigating the matter, adding that the integrity of the voting system of the Dáil was of "utmost importance".

He said he had heard of people asking someone else to press a button for them to vote if they were standing a few metres away from their seat, but not of someone voting for another TD who was not in the chamber.

Minister for Health Simon Harris said it was a "serious matter" that Mr Collins voted on behalf of Mr Dooley.

He characterised their explanations to date as "dog ate my homework territory" and said both TDs "should make statements on Tuesday and answer the questions".

Speaking on RTÉ's The Week In Politics, the minister said that Mr Martin needed to clarify what he intended to do about the controversy.

Fianna Fáil Public Expenditure Spokesman Barry Cowen said Mr Ó Fearghaíl was examining the matter and his findings "will have to be accepted by everyone".

Sinn Féin MEP Matt Carty described the whole affair as "a FF stroke" and said it was not acceptable in any parliament.

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Fianna Fáil's Dooley was absent from Dáil when his votes recorded