The force is withholding £7.3 million of an £8 million down payment after Accenture failed to meet four out of five pre-set milestones, Holyrood's Justice Sub-Committee on Policing heard.
MSPs emerged "battle weary" after senior officers declined to answer questions, sparking accusations from committee members that the Scottish Parliament was being "dictated to" and deflected with "management speak".
Deputy Chief Constable Neil Richardson insisted his staff were not being evasive, but were constrained by sensitive negotiations with Accenture and a need to defer to the i6 project governing board and Scottish Police Authority (SPA) before they can go public.
Police Scotland made its first formal report on the dispute to its civilian watchdogs at the SPA last week, eight months after the first signs of a divergence emerged.
SNP MSP Kevin Stewart said: "You haven't changed the goalposts in any way, so the contractor has failed to meet the obligations of that contract. Is that right?"
Chief Superintendent Alec Hippman, i6 programme manager, said: "I am unable to answer that in public just now in relation to an assertion where they have failed to fulfil their obligation. That is a matter that is going through our due legal process just now."
He said a divergence of view emerged in the first month of the contract in July, forcing Police Scotland to initiate "dispute resolution mechanisms".
Mr Richardson said: "Entering into a public debate about levels of fault is going to do nothing other than potentially compromise the delivery of this, as the supplier will almost undoubtedly seek to defend their position and at the moment, similarly, we would have a position and then this plays out publicly."
He added: "I feel like I am being drawn into a conversation which is potentially going to do damage by putting some information forward which will cause us issues in terms of negotiations."
Committee convener Christine Grahame, an SNP MSP, said: "That puts the committee in a difficult position where we have to hold Police Scotland and the SPA to account and you're saying to us that you are actually not wanting us to challenge anything, frankly."
Mr Richardson said: "That's absolutely not what I am saying. It's simply a case of timing."
Independent MSP John Finnie, a former policeman, said: "If we are scrutinising this we certainly can't be dictated to by internal governance and the timetabling of the SPA meetings."
He added: "I was very dissatisfied with your previous letters, basically because I am not sufficiently minded to learn some of the language that is in there and management speak."
He called for more clear and timeous responses in the future.
Mr Richardson said: "I apologise if previous letters have missed the mark. It's not my intention to be evasive.
"I accept your desire and I will go as far as I possibly can to accommodate that, but my obligation is to ensure that the SPA are involved and we couldn't possibly have something articulated to this committee and in the newspapers before it goes to them."
Ms Grahame, a former lawyer, concluded: "I think the panel and the committee are a bit battle weary."
An Accenture spokesman said its does not comment on customer contracts.
An SPA spokeswoman said: "The SPA receives regular updates on the progress of the i6 programme. The last update was provided by DCC Richardson at our public meeting on 26 February.
"Past ICT projects have encountered more serious long term problems because of a lack of focus in the early stages on agreeing the detailed design.
"At our meeting last week, Authority members were assured that Police Scotland have a strong focus on this and are implementing the lessons learnt from previous projects. We will continue to monitor progress carefully to ensure that the programme delivers the sustainable improvements in efficiency that policing needs."
A previous attempt to integrate the computers of the legacy eight forces, known as the Platform Project, failed at a cost of around £9 million.