Fine Gael Deputy Leader Senator James Reilly has been referred to gardaí by the Standards in Public Office Commission for failing to prove an excess donation was returned to a donor.
According to SIPO's General Election report, Mr Reilly received €1,000 in a cash donation. The maximum that candidates can receive in cash is €200.
SIPO is awaiting confirmation that the excess amount of €800 was returned to the donor.
Speaking on RTÉ's Today with Sean O'Rourke, Mr Reilly said that he declared everything "honestly" and in "in fairness to SIPO they have a job to do".
"I put my hand up, I forgot to give a receipt ... I declared the €1,000, realised the error when pointed out to me and handed €800 back," Mr Reilly explained.
He added that "if there's any upside, it's clear that SIPO are doing their job".
He added that the issue was "nobody's fault but mine".
FG Senator James Reilly says donation breach was his fault after ethics watchdog said he failed to prove an excess contribution was returned pic.twitter.com/BRiKoGIorT— RTÉ News (@rtenews) January 13, 2017
"You do tend to delegate an awful lot when serving in Government," he said.
"The oversight was my fault."
He said that he received the money from a personal friend - a neighbour and he had fully intended to give a receipt to the Standards of Public Office Commission, but due to personal and professional reasons, he forgot.
Mr Reilly said a lot had been going on in his life at the time between contesting the Election, closing a sale on his Co Offaly mansion and going back into medical practice.
He said he did not realise there was a problem until his wife rang him this morning after having heard about the controversy on the radio.
He said that if required he could produce a receipt "by lunchtime".
Meanwhile, the election agent for Fine Gael candidates Jimmy Deenihan and Brendan Griffin was referred after failing to provide detail of their election expenses statements.
SIPO has referred 66 files to gardaí in relation to possible breaches of electoral law from General Election.
The Commission said this morning that donations with a value of over €1,000 were disclosed by unsuccessful candidates.
It said the possible breaches, which it notified to gardaí, included failures to return donation statements, certificates of monetary donations, statutory declarations, statements from a financial institution, or election expenses statements.
Electoral law obliges unsuccessful candidates to disclose donations greater than €600.
Overall, Fine Gael spent €2,768,881 on the General Election and won 50 seats. Fianna Fail, who emerged with 44 seats, spent €1,687,916.
Labour, who went from 33 seats to seven seats, spent €1,083,718.38. Sinn Féin, who went from 14 seats to 23, spent €650,190.
Figures from SIPO also show the Pro-Life Campaign spent more than €40,000 in the General Election last year, with more than half of that spent on advertising.
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