Council bosses were forced to stump up an extra £3.43 million to transform two Leeds schools.
Now a report has slammed the project management team involved and has branded the timescales for the schemes as insufficient.
Plans to turn Carr Manor and Roundhay high schools into centres which could educate children aged four to 18 were expected to cost £2.57m and £4.43m respectively.
But in March last year Leeds City Council had to allocate millions of pounds of additional funding to complete both schemes. The report revealed that the management team was “insufficiently experienced” to deliver whole new modular build schools.
The dossier, which goes before the council’s executive board today, claims that the initial cost reports were based on inaccurate estimates.
Nigel Richardson, director of children’s services said: “We acknowledge and regret that errors during the project development phase of the through-schools at Roundhay and Carr Manor resulted in costs being much greater than we estimated.”
The council approved proposals to extend the age ranges of both Carr Manor High School and Roundhay School to cope with the city’s rising birth rates.
Mr Richardson said: “We welcomed the scrutiny investigation which helped us identify a number of complex reasons for this and highlighted the need for procedural and structural changes.
“The project work was undertaken during a major transitional phase when the management of education in the city was returning to the council’s control.
“Significant changes have since been implemented, which have substantially reduced the risk of anything like this happening again.
“This is an isolated incident.”