A Government watchdog described Sutton Council’s High Street redevelopment project as a failure.

The damning verdict, from Lindsey Mallors, the Audit Commission’s external auditor for Sutton, came at a meeting to discuss the council’s own critical internal audit of its running of the unpopular £3m project.

She stopped short of ordering an external investigation into the project, indicating she was satisfied with the quality of the council’s own audit, and the recommendations it had put forward.

She said: “This is one failure, but is that indicative of failure across all projects?”

At the meeting, at Sutton Civic Centre on Thursday, members of the audit committee accepted mistakes were made on the project that were not indicative of Sutton Council’s usual project management.

The head of the committee, Councillor Tim Crowley, said: “We must be certain a situation like this never happens again.”

The audit showed a litany of errors, oversights and mismanagement, including pushing ahead with features that were dangerous to disabled residents.

Among new failings to emerge at the meeting was council officers missing the chance to spot growing overspends on the project on 15 separate occasions.

The mistakes resulted in a £300,000 bill for Sutton taxpayers, which could have been picked up by Transport for London had it been spotted earlier.

Councillor Jayne McCoy, responsible for the project from May 2010, said: “I welcome the additional scrutiny of our external auditors because mistakes of this kind, even if they are rare, need to be rooted out.

“As a result of the public investigation I ordered, major changes will happen to the way we carry out project and financial management.”

The project remains unfinished, with a living wall of plants near Wilkinsons not installed and planting, working entry gates and tree lights still lacking.

Coun McCoy said: “The costs have already been released, so my job is now to ensure they are completed at best value to the taxpayer.”