Fine Gael's Dara Murphy has resigned his seat as TD for Cork North Central to take up a new role in the European Commission.
The move was announced in the Dáil this morning by Leas-Cheann Comhairle Pat 'the Cope' Gallagher.
In a statement, Mr Murphy said: "Last night, on Tuesday the 3rd of December, I met with the Acting Ceann Comhairle and gave him a letter informing him of my decision to resign my seat in Dáil Éireann.
"I also met the Taoiseach Leo Varadkar last night and spoke to him about my decision. I will commence a new position in the European Commission today."
That position is widely believed to be deputy head of staff for Bulgarian European Commissioner for Innovation Mariya Gabriel.
Mr Murphy has come under scrutiny in recent weeks following criticism over his Dáil attendance and the expenses he has claimed.
He has been largely absent from the Dáil due to a Brussels-based job with the European People's Party, the EU political grouping that Fine Gael is aligned with.
Mr Murphy said today that he would "co-operate with any relevant statutory procedure that may be initiated" into his attendance and claiming of expenses.
Mr Murphy has insisted in recent days that he has been compliant with Leinster House rules following criticism from the Opposition.
A Fianna Fáil complaint against Mr Murphy was submitted to the Dáil's Members Interests Committee last week.
However, given that Mr Murphy is no longer a member of the Dáil, it is likely that the complaint will be referred to the Committee on Procedure and Privilege.
If accepted, it is open to the CPP to empower the Clerk of the Dáil to conduct a review and compile a report.
The first step, however, lies with the Dáil's Members Interests Committee which is due to meet next week to resume its inquiry into voting irregularities by four Fianna Fáil TDs.
The Standards in Public Office said, meanwhile, that "... complaints about a person who has ceased to be a TD (eg resigned their seat), cannot be dealt with by... the Standards Commission".
- Murphy says he has been compliant with attendance rules
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Minister for Justice Charlie Flanagan has said that Mr Murphy had "a number of questions to answer" about his Dáil attendance record and expenses.
He said said it was "incumbent" on Mr Murphy to answer those questions.
Mr Varadkar was more circumspect at the weekend, saying that the record showed that Mr Murphy had attended the Dáil for 120 days and that was the legal requirement.
Asked did he think it was right, Mr Varadkar said "whether it's right or not that's a different matter".
Mr Murphy announced in May last year that he would not contest the next general election.
He was elected to the Dáil in 2011 and previously served as Lord Mayor of the Cork.
Mr Murphy was appointed Minister of State for European Affairs by former taoiseach Enda Kenny in 2014.
He was replaced by Helen McEntee when Mr Varadkar became Taoiseach in 2017.
His resignation poses renewed problems for Mr Varadkar because it further reduces his minority Government's slim numbers in the Dáil.
Last night, the Government only defeated a no-confidence motion in Minister for Housing Eoghan Murphy by three votes and had to rely on the help of three Independent TDs.
Additional reporting Paul Cunningham