Misconduct hearings – most of which collapsed – against teachers in Birmingham accused in the so-called “Trojan Horse” inquiry cost £884,055.
The figures were revealed by the BBC which has fought a Freedom of Information battle with the Department for Education.
The only teacher who was sanctioned – out of 14 against whom the DfE pursued hearings – was the former acting head teacher of Oldknow Academy in Small Heath, Jahangir Akbar.
The case to ban from education the ex-chair of governors for three Birmingham schools that were investigated, Tahir Alam, also cost £387,444 in legal fees.
Several schools in Birmingham were investigated amid claims of a “Muslim extremist” plot to control them, known as the Trojan Horse affair, which began in 2014.
The teachers’ hearings stemmed from that investigation but were dropped when the professional conduct panel of the National College for Teaching and Leadership (NCTL) found its own organisation withheld 25 statements that had been used in an an earlier inquiry led by former counter-terror boss Peter Clarke.
Banned governor Mr Alam told the BBC tghat the cases were a “total waste of public money” that achieved little.
Mr Alam said he was depicted as an “anti-state enemy” during the affair and questioned what the inquiry achieved.
“It was completely unnecessary. Why did they put a banning order on me? I was a volunteer while I was a governor. No school had to appoint me,” Mr Alam added.
He said GCSE marks at the schools where he was chair of governors had declined since the affair.
Mr Alan said the process had damaged his reputation, career and friendships.
“It was stressful. It’s hit me economically. I can’t do what I love doing. I spent 20 years building my skills. Within the Muslim community, people who’ve always known me, regard me as a hero overall. But from people within the education fraternity, I’m cut off. People don’t want to associate with me because they think it will harm their careers.”
The DfE said it was “looking carefully” at the handling of the cases, which were “led by an external law firm.”
It said: “We have taken strong action and continue to act to prevent extremism from gaining a foothold in our schools – in Birmingham and across the country.”