Sinn Féin's chief negotiator, Mr Martin McGuinness, has accused the PSNI of a "determined campaign" to discredit his party.
Mr McGuinness was speaking on his way to a meeting with the Taoiseach, Mr Ahern, in Government Buildings in Dublin this evening.
He said he believed there were former RUC members within the PSNI doing their utmost "to undermine Sinn Féin's participation in the peace process". The campaign to "paint as black a picture as possible of republicans" was being orchestrated by elements within the security forces who were "hostile to the peace process", he claimed.
Mr McGuinness said he intended asking the Taoiseach during their meeting this evening to make the point to the British government that the PSNI campaign against SF must be stopped.
Responding to a warning issued by Mr David Trimble that his party would pull out of talks on the review of the Belfast Agreement next week unless action was taken against Sinn Féin, Mr McGuinness said such comments were unhelpful.
He accused Mr Trimble of "spouting off at the mouth in Westminster" and trying to 'out-Paisley' the Rev Ian Paisley.
Mr McGuinness said past experience of progress within the peace process showed movement can only be made through dialogue.
Speaking in the House of Commons today, Mr Trimble demanded sanctions against Sinn Féin over the alleged involvement of the Provisional IRA in the abduction and beating of a dissident republican in Belfast last week.
Four men were arrested last Friday in Belfast after Mr Bobby Tohill (45), a well-known dissident republican and former Irish National Liberation Army member, was found bound and badly beaten in the back of a van. He had been abducted from a city centre bar a short time earlier.
In a statement, An Phoblachttoday said it has been told by republican sources that "the IRA did not authorise any action against Bobby Tohill". The four man have been charged with abduction and grievous bodily harm, but a charge of IRA membership was not proceeded with.
Mr McGuinness asked "why was that [dropping the membership of the PIRA charge] done?" before suggesting it was because the Police Service of Northern Ireland wanted to "capture the weekend headlines."
He also said he supported Mr Ahern's assertion that all paramiliarism must end "but it's one thing saying that, and another making it happen."
