An academy trust that runs 10 schools in England has been accused of making false claims for government grants.
BBC Panorama has found the Bright Tribe Trust received public money for building work, lighting upgrades and fire safety improvements that were either not finished or never done.
New trustees, appointed at Bright Tribe two months ago, have now commissioned independent investigations.
The trust says swift action will be taken if rules have been breached.
Panorama reveals how Bright Tribe was given £566,000 to demolish and rebuild unstable walls in the sports centre at Colchester Academy in Essex.
But instead of knocking down the dangerous walls, the trust carried out a cheap repair using metal braces.
An insider has told Panorama the repair job only cost about £60,000, but paperwork obtained by the programme shows that Bright Tribe received the full £566,000, and falsely told the government the work had been completed.
Bright Tribe also failed to carry out essential fire protection work, including the fire-stopping of a ceiling void and installing over 100 fire doors in another government-funded project at the sports centre.
The trust again claimed the full £255,000 of funding, despite being warned by school staff that the work had not been completed and the building was still unsafe.
Staff emailed Bright Tribe saying: "The void above the ceiling has never been completed and is a fire hazard as it is completely open. If there is a fire this will spread throughout the building."
Panorama has also discovered that the trust made false claims for grants for the Whitehaven Academy in Cumbria.
Bright Tribe claimed £320,000 for energy-efficient lighting, when less than a third of the lights have been installed, and a further £202,000 to upgrade school boilers.
Instead of installing new boilers, the trust moved some old boilers from a disused part of the school.
An independent engineer, who inspected the school in July, concluded that the work carried out should have cost far less than was claimed from the government.
Local Conservative MP Trudy Harrison said she was shocked by the programme's findings: "Lights haven't been fitted, work hasn't been carried out.
"We need some common sense applied to this. I am a Conservative MP and this is our party policy, but I am speaking out because it is wrong."
The government was warned about problems at Bright Tribe in 2015.
Northern hub of academies
It investigated and found serious failings, but instead of imposing financial sanctions it gave the trust an additional £1m grant the same year.
The cash was to set up a northern hub for academies in the north-east of England, but last December Bright Tribe announced it was pulling out of the project. The £1m has not been repaid.
When the government asked the trust to account for the £1m grant, Bright Tribe said the vast majority had already been spent on salaries and provided a list of staff who - it said - had worked on the project.
Panorama has obtained the list and spoke to people whose salaries had been claimed against the government grant. Several of these individuals said they had never worked on the northern hub project.
Northumberland County Council, which is responsible for schools in the northern hub area, has been trying to get back some of the public money.
Conservative councillor and deputy leader of the council Wayne Daley said the government was to blame for failing to safeguard the cash.
"That is a complete dereliction of duty to our community here and to the public purse. This can never ever be allowed to happen again. Ever. I'm genuinely shocked, I really am."
Bright Tribe was set up by businessman Michael Dwan, who made his reported £114 million fortune from private contracts in the NHS.
In total, Mr Dwan's companies have been paid £8m for services by Bright Tribe and another trust he set up called the Adventure Learning Academy Trust, which runs five schools in Cornwall.
He says he has donated close to £2.4m to the trusts and that all the work carried out by his companies was done at cost or less.
In an interview with Panorama, Mr Dwan said: "The cost of providing the £8m in work and services was £10.5m. So actually we made a loss.
"I received some revenue, but I made a loss. And throughout the whole period I never, ever, made any profit. I made a substantial loss."
Mr Dwan insists he didn't control the trusts because he was never a trustee.
"I am not in control of the trusts and never have been. I am a very, very interested observer. I have never had any authority, never any decision-making power and no vote."
Mr Dwan wasn't technically a trustee himself, but his charities controlled the trusts and he chaired board meetings as their representative. Panorama has spoken to numerous insiders who say he made all the key decisions.
The grants provided for the work at Whitehaven were based on estimates provided by one of Mr Dwan's companies.
Mr Dwan's company Blue Support then handed the contracts to a company owned by a close associate of Mr Dwan, which then sub-contracted the work straight back to Blue Support Services.
Mr Dwan told Panorama that all of the grant money had been spent at the schools, and that his companies had made a loss on the work.
Academies minister Lord Agnew said academies had to provide more financial information than other schools and that more than 95% of trusts had no issues.
"We take the use of public money very seriously and will not tolerate those who try to exploit the system for personal gain," he said.
"But I am clear that Bright Tribe Trust is not representative of all academies, and more than half a million children are now in good or outstanding academies that were typically previously underperforming schools, thanks to innovative trusts across the country."
Mr Dwan's lawyers say the programme's allegations about the Northern Hub are untrue and that a full government audit has been completed and no issues have been raised with Mr Dwan.
They said "each and every allegation raised by the BBC" is completely denied.
You can watch 'Profits Before Pupils? The Academies Scandal' on BBC iPlayer: https://www.bbc.co.uk/programmes/b0bk5q99