The cost of a Derby road improvement scheme being delivered by Galliford Try has more than doubled since work started 10 months ago.
Derby City Council confirmed the budget for the A52 Wyvern improvement programme had increased to £33m – £18m higher than the original £15m estimate given last year.
Galliford won the £9m contract for the Wyvern project last October under the Midlands Highways Alliance framework.
However, in May the emergence of delivery issues prompted a review of the scheme.
A statement by Derby City Council chief executive Carole Mills said: “In May this year, issues were identified with the scheme.
“This included differences between the budgeted costs and the emerging estimated committed costs, which resulted in potential delays in delivering the scheme.”
The review found the issues were “more complex than originally envisaged” and the council increased the approved operational budget to £33m to “ensure work could continue in a timely manner”.
Work on the project was originally scheduled to complete in March 2019, but the council announced in June that this would be delayed by at least three months.
The local authority has also now confirmed that its independent audit service has begun an investigation into the project.
It aims to produce a final cost estimate by late autumn.
Ms Mills said: “I want to emphasise how seriously we are taking these failings. The council is committed to finding out and fully understanding what went wrong and to delivering the scheme.
“Derby citizens and council tax payers should have every faith that this issue will be resolved and the benefits of this key infrastructure project will be realised.”
A Galliford Try spokesman said: “We’re currently working closely with Derby City Council to understand more clearly the reasons for the increased costs and how they can be mitigated.”