Alastair Stewart had previously been warned by ITN bosses about his inappropriate Twitter activity before his decision to step down after 40 years earlier this week.

Insiders at the news organisation stressed yesterday he had not left because of one isolated tweet, but because of a series of ill-judged remarks to both Martin Shapland and others, all of which breached editorial guidelines.

One insider said: “Alastair was already drinking in the last chance saloon over his social media comments and this was simply the final straw. This is not about one Tweet that has become public, but multiple breaches. It’s a real shame.”

The source said there had been a “sustained exchange” of inappropriate messages between Stewart to Shapland, a policy manager. They added: “This is not the first time he’s been spoken to about the way he conducts himself on social media. The suggestion that he's lost his job over one Tweet is simply wrong."

(Image: CAMERA PRESS/Nick Gregan)

In a statement issued on Wednesday, Stewart admitted he’d made, “a misjudgement which I regret”.

But he stopped short of apologising to Mr Shapland over his decision to to use a Shakespeare quotation from Measure to Measure during a spat about the monarchy in which a man is compared to “an angry ape”.

Mr Shapland said Stewart was “a disgrace” for insulting him while hiding behind the verse. And ITN issued a statement saying Stewart was stepping down from his role following “errors of judgment in [his] use of social media”.

Yesterday, some colleagues called on bosses to reinstate the newsreader.

(Image: ITV)

Ranvir Singh, the political editor of Good Morning Britain, said: “I would never use the word racist and his name in the same sentence. I have sat with him for hours and hours and hours, days and days and days, years, and he has only ever been gracious and encouraging to me. We have had talks about how he and his wife have felt proud of what I have achieved.

She added: “In my gut, I would put my house on it that not for one second did he write that quote thinking that it was in any way a slur on someone’s skin colour.”

GMB host Ben Shephard said: “I’ve been lucky enough to work with Alastair over the years as well, and he’s an extraordinarily generous person with experience as a broadcaster to work with.”

(Image: Twitter)

Andrew Neil wrote: “Alastair Stewart - very smart, kindly, professional, impartial, knowledgeable, fun... Now the only person to be fired for quoting Shakespeare accurately. The only explanation can be the ITN suits wanted him out - and seized their chance.”

Broadcaster Katie Derham wrote: “So very sorry to hear the news about Alastair Stewart stepping down from ITN.

“A very dear friend and colleague; enormous fun and extremely supportive, and unbelievably well informed. He will be missed.”

Many of the posts to Shapland, have now been deleted. But other broadcasters rallied to support the veteran newsreader, saying they were “pretty appalled” about the “ignominious end to his career”.

(Image: @MShapland/Twitter)

One – who asked to remain anonymous - moaned: “If they just wanted rid of him, which these days just happens because you’re a bit old and a bit expensive, there are other, fairer ways.

“He’s senior, he’s well loved. He’s somebody who should have left in a blaze of glory.

“He’s one of the greats... It’s this quite modern idea that you get cancelled for saying just one thing.

“Very, very senior journalists, broadcasters who either worked with him or know him through their jobs, are pretty appalled that this has happened to him.”

(Image: @MShapland/Twitter)

But the colleague conceded that Stewart had made mistakes. “Was it a very stupid thing to do? Yes. Was it insensitive? Yes. I can’t imagine that for a second he meant that in a racist way.

“He certainly should have apologised of course. He could have apologised, come off Twitter, there are ways of showing mea culpa without having to end his career over it.

“He was a prolific tweeter and did get into battles all the time on Twitter. There should have been a warning before you sack him, saying, ‘This is getting a bit much’, rather than just this.”

Friends of Stewart’s last night said that, despite a lengthy one-on-one exchange with Shapland about the relationship between the Crown and taxpayer funds, he hadn’t noticed from Shapland’s profile picture that he was black.

(Image: Twitter)

Yesterday Shapland said he took “no pleasure” in Stewart leaving his post.

He said: “There was not a single post as has been widely reported, but several posts - which have all now been deleted.

“I understand that Mr Stewart has acknowledged the words he used were misjudged and has expressed regret at what happened. I thank him for that.

“No-one is perfect. We are all human and we all need to learn from our experiences and mistakes and try to be better people in the wake of them.

“An apology and commitment to be more careful about language was all that I would have asked. It is regrettable that he has decided to stand down and I take no pleasure in that.”

Critic Kate Maltby, who read all of the tweets between the pair, said: “I watched the actual exchange in real time - and it was much, much nastier than has been reported. It wasn’t just the ‘ape’ quote.”

The statement said that the decision to quit was “supported by both ITV and ITN” and had been agreed by Stewart, who joined the news organisation in 1980 as industrial correspondent. In it, he said: “It was a misjudgment which I regret, but it’s been a privilege to bring the news to households throughout the UK for the past 40 years.”

Stewart, a part-time freelance presenter who fronted the lunchtime and weekend news bulletins, has since deleted his Twitter account.