Sinn Fein has called on the Taoiseach to make it clear to the British government that the Northern Secretary's approach to the Police (Northern Ireland) Bill is "totally unacceptable".
Mr Ahern is due to hold a telephone conversation with the British Prime Minister, Mr Tony Blair, on the subject today after the Bill was introduced in the British House of Lords yesterday.
Introducing a 100-page analysis document, Policing: A New Beginning?, which is highly critical of the Bill, Mr Martin McGuinness of Sinn Fein said that while he was "very satisfied" with Mr Ahern's comments expressing unhappiness at the incorporation of the RUC's name into the title of the new police service, it was vital for him to leave Mr Blair in no doubt that the Patten recommendations had to be implemented in full.
"The problem now is that the British government disingenuously seeks to locate compromise as being somewhere between their proposals and the Patten recommendations, when many nationalists have made clear that, for them, Patten is itself the compromise," Mr McGuinness said.
The Sinn Fein document, which has been passed on to both governments as well as the US administration, concludes that of the 175 Patten recommendations only 11 are being implemented, while 89 have been "subverted" and there is insufficient information to judge the remaining 75.
According to the party, the main points of departure from Patten concern the legacy of the RUC, including the name, badge and symbols, the powers of the Police Board and of the ombudsman, the oath and issues of local accountability.
Referring to an interview in yesterday's Irish Times with a former member of the Patten commission, Dr Gerald W. Lynch, in which Dr Lynch said the Bill went directly against the wishes of the commission and would discourage young nationalists from joining the new force, Mr McGuinness said:
"This is a touchstone issue not just for republicans but for nationalists and society as a whole. We are the elected representatives of a community that wants to be policed. They do not want to live in a jungle and want to be part of building a new future for themselves and for their children."
While the British government had moved the proposals back some way in the direction of Patten, they still fell far short of the Patten recommendations, he added. "If Mr Blair is genuine and sincere about bringing about a new beginning in policing, he has to recognise that the nationalist community has to be on board. If he fails on such a touchstone issue as policing, history will treat Mr Blair and [the Northern Secretary] Mr Mandelson very badly."
Mr McGuinness insisted Sinn Fein was not an "anti-police" party, saying it was "very passionate" about creating a new police service. Asked whether Sinn Fein would withdraw from the Belfast Agreement if its demands in the policing debate were not met, he added:
"The issue goes to the heart of the whole process. If the British government fails to address it, they are making a huge mistake. A police service which only satisfies rejectionist unionists, who want to destroy the Belfast Agreement anyway, is useless."
If the legislation was returned to Patten, the party would study it carefully and have a "sensible, reasoned discussion" on whether it would back the new service, Mr McGuinness added. A Northern Ireland Office spokesman yesterday rejected Mr McGuinness's criticism, saying the British government "simply did not recognise the Bill in the description offered by Sinn Fein."
"The legislation will faithfully implement Patten. A new beginning to policing will be made, starting with a new name, the Police Service of Northern Ireland. All those committed to change and genuinely interested in effective policing will be able to support the Bill when it completes its passage through parliament," he said.
The SDLP MLA for west Belfast, Mr Alex Attwood, said his party remained far from being in a position to recommend nationalist participation in a future police service.
"The Bill remains deficient, not just on cultural issues of flag, name and badge but also on structural issues of human rights, independence of the Policing Board, accountability of the police and on the pace of policing change," the SDLP policing spokesman said.
Ulster Unionist MP Mr Jeffrey Donaldson accused the British government of having "made a mess" of the Bill and said if it "pandered" much more to nationalists, there could be "enormous pressure" on unionists to withdraw from the Assembly.
"The [British] government has made a mess of this matter. Bearing in mind that its aim was to create a police service with widespread community support, it is clear these proposals do not in either community," he said.