The civil engineering contractor paid the county council £33m last year in an out-of-court settlement, which included defects known about at the project’s completion date.

But a new technical report has outlined the need for up to £31m of extra repairs not uncovered at the time of the settlement.

A second legal battle would come at an awkward time for BAM Nuttall. The parent Dutch Group is presently reviewing the UK and German business as part of an £80m cost-cutting drive.

BAM was two years late in handing over the project and originally claimed the council owed them around £70m more than the £84m contract price. But the settlement saw the council pay the original contract value with BAM footing the difference.

The latest technical report for the council outlines that some parts of the guided busway were either not built to the agreed design or don’t comply to national standards specified in the contract.

Bob Menzies, Service Director, Strategy and Development, said: “The technical and legal advice is that these defects were created or left by the contractor and they should be fixed.

“More importantly this should be paid for by Bam Nuttall.

He added: “The Busway is a highly successful transport system that reached its passenger targets early and is used for millions of journeys.

“We have fixed some of the defects but the advice is if we leave them then beams could move seriously effecting ride quality. The Committee will look at this independent expert advice and make a decision on the best way forward.”

The council has estimated costs of £5.3m for a fresh legal battle with BAM Nuttall over the latest problems, but hopes the dispute will not reach court.

Councillors will hear that the legal advice believes BAM is in breach of contract and that the Council has a good case and should pursue the contractor for the money to pay for the necessary repairs.

A decision on how the council will proceed will be taken on Tuesday.