The chairman of governors at a troubled city grammar school has hit out at “unsubstantiated allegations” made about senior staff on Facebook.

In a strongly-worded letter to parents of pupils at Simon Langton Girls in Canterbury, Alisdair Chisholm has declared “enough is enough”.

He has urged them to ignore “false” posts on the social media site, claiming the allegations “compromise the reputation” of a school which has been roundly criticised in recent weeks.

Its head teacher, Jane Robinson, resigned earlier this month, shortly after the conclusion of a confidential investigation into complaints about her treatment of staff and pupils.

Mr Chisholm is thought to be one of only a handful of people to have seen the findings of the secret probe, which he refuses to make public.

After reviewing the report he decided “a number of actions should be put in place”, but has yet to reveal what they are.

But he has been quick to address comments about the employment of teaching staff made on the Langton Girls’ Facebook parents forum.

In the letter, he says: “Over the past few weeks a series of Facebook posts have made unsubstantiated allegations maligning senior staff and teachers; inappropriately sought background information about recently recruited staff and speculation about an entirely confidential school matter, complicating and potentially compromising a process.

“The suggestions made that some staff are ‘implicated’ in outstanding matters is simply false. All staff in our school have been hired through correct processes.”

Mr Chisholm, who replaced the departing chairman Ash Rehal last year, has himself come under fire, not least for his decision to keep the investigation report under wraps.

“Over the last six months, as chair of governors, I have simply ignored the posts about myself and the vice chair,” he wrote.

“However, enough is enough, and I will not stand by and see the hard-working and dedicated staff of our school maligned in this way.

“Beyond the unfairness of it, these types of posts cause stress and can cause illness, and surely compromise the reputation of the school.

“I condemn these posts without qualification and ask that they stop. I urge you to continue to support our amazing school and dedicated staff.”