The Taoiseach has told the Mahon tribunal he never received any sum of dollars and that leaks of tribunal documents before the election were "explosive" and intended to damage him personally and politically.
Mr Ahern said he also "totally and utterly" rejected the "false allegations" made by developer Tom Gilmartin that he took money from Cork-based developer Owen O'Callaghan. He said these allegations were "not based on anything other than hearsay".
On the basis of those false allegations he had been the subject of unprecedented attack on his integrity and honesty, he told the inquiry.
Mr Ahern told the tribunal, during the first of two days of evidence, the false allegations "have been calculated to do me enormous personal and political damage".
He said that after 10 years of investigation into his affairs there was no evidence he had engaged in any corrupt practice.
The Taoiseach said he had never taken a bribe in all his years in politics and insisted a lodgement of almost £30,000 in December 1994 was sterling and not $45,000 as claimed by the tribunal.
Mr Ahern said that at his interview with the tribunal, the theory that the lodgement was dollars was never put to him. It was also not surprising, he said, that he could not remember all the details of the transactions involved "at this remove".
The 1994/95 period had been a time of great personal turmoil and of significant demands on his time as he attempted to rebuild a "deflated" Fianna Fáil party.
The Taoiseach said the lodgments of December 1994 took place over a period when he had "suffered the disappointment" of not being elected Taoiseach in "strained and unexpected circumstances".
Concluding his statement, Mr Ahern told the tribunal: "I have done nothing improper. I have done no wrong."
Taking the stand at the tribunal at 10.30am, Mr Ahern's counsel asked that that the Taoiseach be given an opportunity to make a statement before he gave his evidence. Chairman Alan Mahon said this was not normal practice, but he granted permission.
Mr Ahern read from a prepared statement outlining details of a number of financial transactions under investigation by the tribunal.
He said he had engaged a currency expert who had proven that the December 1994 lodgment about which his former partner Celia Larkin was questioned yesterday could not have been dollars.
After Mr Ahern's statement, he was questioned by Des O'Neill SC for the tribunal. Mr O'Neill put it to the Taoiseach that it would have been preferable if he had given the lengthy statement he made this morning to the tribunal beforehand.
Mr Ahern said he did not believe the tribunal would deny the fact that he had had to deal with these issues in the public eye. "It seemed a reasonable request, and I am grateful for the opportunity," he said.
Mr O'Neill said he did not want to cut Mr Ahern short in his responses to questions but that the testimony would take less time if they did not become engaged in "side issues".
"That applies both ways, does it?" Mr Ahern replied.
The tribunal is investigating four bank lodgements to AIB O'Connell Street, Dublin, totalling over £84,000 in 1994 and 1995. All of the lodgements were preceded by foreign exchange transactions.
Bank officials at AIB gave evidence over seven days in July. Mr Ahern's former landlord, Manchester businessman Michael Wall, was questioned on Tuesday.
The tribunal heard this week that Mr Wall gave almost £30,000 in sterling notes to Mr Ahern in December 1994. The money was intended to refurbish a house in Drumcondra that Mr Wall planned to buy and later rent to Mr Ahern.
Tribunal lawyers believe that cash later lodged by Ms Larkin equated exactly to $45,000, based on exchange rates at the time.
Members of the public began assembling at Dublin Castle at around 7.30am, and the public gallery at the tribunal is full.