Renfrewshire’s Provost said it was a “sad and sorry day” for the council as the damaging findings of a review into the errors which saw Dargavel Primary School built too small were discussed.

The botched calculations for the building in Arrochar Drive, Bishopton, have left a bill on the table of up to £75 million for a second primary school and an extension for Park Mains High School.

An investigation into the catalogue of errors, which was conducted by a former chief executive of four councils in David Bowles, examined the Section 75 agreements between the council and landowner BAE Systems.

It uncovered a series of damning discoveries, including that senior education management at the time was “incompetent”, “repeated failure” to test data, and a suggestion officers showed “professional arrogance” in response to concerns.

Councillor Lorraine Cameron, the civic head, said it was her “duty” to apologise for the circumstances that led to the probe being carried out by Mr Bowles.

At Thursday’s meeting, she said: “A whole community has been created in Bishopton and it’s the size of a small town.

“This should have been a huge success story for Renfrewshire, instead it is tainted by what some call ‘mismanagement on a seismic scale’.

“These failures encompass different departments of the council, various different political administrations and several staff members who are no longer with us – no longer employed here.

“It leaves us in a very difficult and frustrating position. It is a sad and sorry day for Renfrewshire Council, but make no doubt about it, we will be judged by this shambles but we will also be judged by how we deal with it.”

Mr Bowles said his report makes “very difficult reading” for the council and for the residents, explaining that by 2018 there was “ample evidence … that something was wrong” in relation to the calculations.

However, he reflected that there was “no sign of any single concern ever having been looked at.”

“I find that absolutely extraordinary,” he added.

It was disclosed at the meeting that BAE will be expected to meet half of the cost of the extension for Park Mains, with the council planning to increase its capacity from around 1,600 to 2,000 – at a fee of between £27m and £30m.

However, the developer is not legally obliged to contribute to the delivery of the new primary school, which is expected to cost between £42m and £45m.

But it has been asked whether it would consider making a voluntary contribution.

Alan Russell, chief executive of the council, also confirmed he had been in “regular dialogue” with the Scottish Government to explore all funding avenues that might be available.

He said: “I am deeply sorry for the historic mistakes made by previous senior officers over a prolonged period.

“I apologise for the very understandable distress this has caused to our local communities in the area and particularly to those within the communities who raised well-articulated concerns over many years.

“Such concerns have been proven to be entirely justified. They were, however, not listened to and they were unacceptably dismissed by previous senior officers.”