A £46m project to build an IT system for Police Scotland collapsed because of a loss of trust and disagreements about what it needed to achieve, auditors have said.

The i6 programme was expected to help the force save around £200m over ten years.

Contractor Accenture, however, underestimated the complexity of the programme and the resources needed to develop it, according to a new report from Audit Scotland.

"The i6 programme had difficulties almost immediately after award of the contract," auditors said.

"Within weeks of starting the high-level design phase in July 2013, there was a difference in opinion about the search function within i6.

"The i6 programme team believed that the functionality of Accenture's solution did not meet the requirements it had agreed in the contract."

Police Scotland, the Scottish Police Authority (SPA) and the Scottish Government challenged Accenture about the problems but were given assurances that the system would be delivered.

Audit Scotland found good practice was followed in the planning and procurement of the i6 programme.

Fundamental flaws and serious errors only became clear when the IT system was handed over to Police Scotland for testing in August 2015, auditors said.

The programme was terminated in July 2016 and the SPA agreed a £24.7 settlement with Accenture, under which the firm agreed to refund the £11.1m which the SPA had paid and make an additional payment of £13.6m.

Auditor general for Scotland Caroline Gardner said: "Modern policing faces financial and operational challenges.

"Given the role that i6 was to play in police reform, there is an urgent need for a frank assessment of Police Scotland's IT requirements and how these can be delivered alongside the vision set out in the recent Policing 2026 draft strategy."

Martin Leven, director of ICT at Police Scotland, said: "i6 was an important element of Police Scotland's ICT plans - but not the sole element.

"Since 2013, more than 30 national applications have been implemented successfully.

"This includes replacing or upgrading a significant amount of outdated hardware and real progress has been made towards the delivery of a new national network and standardised modern national desktop computers."

A Scottish Government spokesman said: "We welcome the publication of the Auditor General's report, which helpfully outlines a number of areas of good practice as well as factors behind the decision to terminate the project, enabling police and other public services to learn from these conclusions."