Ms Devitt, one of two party councillors criticised in the report over payments linked to developments, quit the party last night.
Mahon found her actions “entirely inappropriate”. It said she acted as a legal consultant to a property group with the promise and payment of £20,000 but she was also an elected Dublin councillor and on a health board.
In a statement, she said: “The references to me in the Mahon Tribunal Report are inaccurate. I have never, ever done anything that conflicted with my role as a councillor or that impinged on my duty to the constituents I have represented for over 26 years. I am confident that this issue can be corrected.”
Mahon also found that Dublin councillor Therese Ridge received an “inappropriate” £1,000 payment from lobbyist Frank Dunlop, that she supported the Quarryvale project, and was “handsomely rewarded” for her efforts.
Ms Ridge said she would “absolutely” not resign.
“It’s [the tribunal finding] quite strange as I didn’t vote for Quarryvale and I got the payment in 1992 after the vote.”
She said the cheque arrived “unexpectedly” and that she was glad to receive it as there were other candidates in an area “where it was hard to hold onto the seat”. She said she had accepted a political donation and was a truthful person.
TD Olivia Mitchell, who received an “inappropriate” £500 donation from Mr Dunlop as a councillor, did not return calls last night.
A senior Fine Gael source said he expected a resolution to an internal inquiry into the payments by Easter.