Sinn Féin and the SDLP today traded blows ahead of a House of Commons debate on the Northern Ireland policing bill.
Westminster is due to consider the Police (Northern Ireland) Bill, bringing forward additional reforms which helped secure the SDLP's participation on Northern Ireland's Policing Board.
Sinn Féin's Mr Gerry Kelly claimed the bill threatens "three years hard work and negotiation" by his party.
As MPs prepared to debate the additional measures, including a proposal that ex-paramilitary prisoners should sit on district police partnership boards, Mr Kelly accused the SDLP of insisting at the Weston Park talks in 2001 additional police legislation was impossible.
The North Belfast MLA said: "The SDLP told us before Weston Park that amending legislation was not possible, yet it was delivered and more recently they told us again that new legislation was not possible. Yet again it has been delivered.
"Had the SDLP held its nerve and not settled for less than Patten then perhaps we would have achieved the new beginning to policing by now."
However SDLP Policing Board member Mr Joe Byrne hit back, claiming Sinn Féin had started to shift onto his party's ground.
Referring to a newspaper quote from a Sinn Féin spokesman that "policing is wider than legislation," the West Tyrone MLA countered: "The SDLP has been making this point for months.
"Time and again we have said that everyone should be on the Policing Board ensuring that Patten is implemented.
"Sinn Fein rejected this. We made the point that not going on the board until all of Patten was implemented was like refusing to join the (power-sharing) executive until all of the Agreement was implemented.
"Sinn Féin belatedly has come to accept the SDLP view. This is further confirmation that as Sinn Féin prepare to jump, they jump very late."