Three trade unions - Unison, GMB and NUT - have joined forces calling for Hackney Council to lift “gagging” orders so that ex-staff from the five schools run by the suspended so-called “superhead” Greg Wallace can give evidence in an investigation.

Mr Wallace – once described as one of education secretary’s Michael Gove’s “magnificent seven - was suspended from his post in July while the council investigates allegations over the awarding of lucrative computer contracts to C2 Technology, which is reportedly owned by his boyfriend Tony Zangoura.

But this week The Hackney branches of GMB, Unison and the National Union of Teachers (NUT) called on the Learning Trust for an investigation to dig deeper.

They say many staff working at the BSF schools have raised concerns about workload and working conditions, as well as allegations of what happened during OFSTED inspections and when SATs tests were conducted.

“In-light of the other allegations which have been raised by our members, the high turnover of staff and large numbers of compromise deals, we are requesting a full investigation into the BSF by the Learning Trust,” they say in a letter signed by Sandra Hall from the NUT, Matthew Waterfall from Unison and Tony Brown from the GMB.

Compromise deals are contracts drawn up between an employer and employee which grant the employee a sum of money in return for agreeing they will have no further claim against the employer, waiving statutory claims like unfair dismissal, discrimination or entitlement to a redundancy payment.

Branch Secretary of Hackney Unison Mr Waterfall who oversees compromise deals for his members told the Gazette: “Lots of people were gagged and paid off, I don’t think I’ve done as many compromise deals through the council, which has 3,500 staff, as I have done through Greg’s schools.”

Gagging clauses in severance packages - which stopped departing NHS staff whistleblowers from speaking out about patient safety or care - were banned by the government in March.

Mr Waterfall added: “I am worried they (the council) won’t do a proper investigation, I don’t think there’s a very good record in this borough of people in positions of high office going through the same process as lower paid staff who do things wrong.

“I don’t think money’s an issue, I don’t think it’s in the interests of any organisation whether it’s Hackney Council or the government to put their executives and their top people through a process which potentially gets out to the public, because it makes it look as though they don’t run an effective organisation.”

Mr Wallace started out as head teacher of Woodberry Down in 2001, and was deemed so successful he was drafted in to turn four more underperforming schools around– London Fields in Westgate Street, Whitmore in Bridport Place, Hoxton, Mandeville in Oswald Street, Lower Clapton and Burbage in Ivy Street, Hoxton.

They all eventually came under the umbrella of the Best Start Federation (BSF), whose governing body the council has withdrawn financial and staffing powers from.

Mr Wallace refused to comment, but Jane Kemsley, the BSF’s acting vice chair of governors said the BSF, under Mr Wallace’s leadership, had transformed five previously failing schools thus helping thousands of children in Hackney.

She continued: “Hackney Learning Trust has recently judged leadership as outstanding in all the schools.

“The success we have achieved for children has been dependent on ensuring we have the best possible teachers in our schools and we make no apology about moving on staff to secure high standards.”

A council spokesman said compromise agreements are legally binding on both parties and the council has no authority to set them aside.

“If unions have concerns about the compromise agreements they have signed on behalf of their members then this is a matter they can address through their own procedures and advice,” he added.

The schools, which wanted to convert to academy status in May, but had to put the plan on hold once the investigation was launched in April, appealed to Mr Gove to intervene in the case. He refused.

NUT members at Whitmore walked out for two days in March 2011 over workload.