City Hall staff have had to be offered counselling following a torrent of abusive letters and emails directed at Sadiq Khan and the Greater London Authority, it has been revealed.

Speaking at a meeting of the London Assembly’s GLA oversight committee on Tuesday, Ali Picton, the Mayor of London’s director of operations, revealed that staff have had to refer correspondence to the police over “offensive, inappropriate, threatening” content and “messages of hate”.

Ms Picton said that it is “a damning indictment” that City Hall has had to offer staff counselling due to the “shocking” and “disgraceful” content they have seen aimed at Sadiq Khan.

She said: “I would like to pay tribute to the people that have to deal with this correspondence in our public liaison unit, and also in my own team, because they really do see some stuff that is shocking and, frankly, disgraceful.

“I think it is really positive that City Hall has offered – I mean, it’s a damning indictment– we’ve had to offer counselling to a number of members of staff that have to deal with this. I’m really pleased that we do, but I think it is important and I would like to pay tribute to the work that they do day in, day out to deal with this level of correspondence.”

Susan Hall, the leader of the City Hall Conservatives, told the meeting that she was “appalled” that staff and the Mayor of London have been subjected to such levels of abuse.

Ms Hall said: “I am appalled, as you are, that some of the letters that come into the mayor are abusive in that way, and I’d imagine that will go for every single Assembly Member. I think it is an absolute disgrace if they are as you say, which I have no reason to believe they’re not.”

Last year, Sadiq Khan revealed that he requires a team of 15 police officers to provide 24/7 security for he and his family “because of the colour of his skin and the god he worships”.

Mr Khan told the Labour Party conference in September that he is “not going to allow these racists and these Islamophobes to intimidate me” and that he will “never bow to them”.