It is withholding £7.3m of an £8m down payment after Accenture failed to meet four out of five pre-set milestones.
Senior officers declined to answer questions at the Scottish Parliament's Justice Sub-committee yesterday.
It led to accusations Holyrood 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 and a need to defer to the i6 project governing board and Scottish Police Authority (SPA) before they can go public.
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."