A series of problems caused Aberdeen's Diamond Bridge to open months late and cost millions more than planned, an inquiry has revealed.

The first cars crossed the Diamond Bridge over the River Don in June, seven months later than expected.

The project, popularly known as the Third Don Crossing, was expected to cost £15.5m but its budget eventually rose to about £22.3m.

Issues during the construction of the crossing prompted a review by the council's external auditors.

Their report, published on Wednesday, said problems arose when a key member of staff suddenly went on sick leave at a critical stage.

They said a "silo approach" taken by the council - where workers avoid sharing information outside their own department - meant it took longer than necessary for staff to take on their additional duties.

Auditors said the council's decision to build the bridge using a "works only" contract meant it had shouldered a larger share of the financial risk.

They said the 2013 report which councillors based this decision on was "very light on detailed analysis of the risks".

Auditors also questioned the short time companies were given to submit bids for the contract and said it was "surprising" their offers were assessed on the basis of cost and not quality.

Problems with uncharted utilities uncovered during construction caused delays and pushed costs up because the council "struggled to get utility companies to respond in a timely manner", auditors said.

They concluded: "There was no one specific element that resulted in the late delivery and cost overrun on this project however, as the report highlights, there were several factors that influenced that situation.

"Like all change processes, success will be driven by the provision of clear leadership, adequate resources with the right skills and a clear action plan.

"From discussions with a number of stakeholders it is clear that many of these building blocks have already been established or are actively being rolled out across the organisation."