The Guardian’s publication of an “antisemitic” cartoon highlighted failures in their editorial process, the newspaper’s editor-in-chief has said in an internal email.

In a message to editorial staff sent on Wednesday afternoon, Katharine Viner condemned the “completely unacceptable cartoon” that contained “a number of offensive antisemitic tropes”.

The sketch, drawn by artist Martin Rowson, showed former BBC chairman Richard Sharp with “outsized, grotesque” features clutching a box that held a squid, Rishi Sunak’s head, and what appeared to be gold coins.

At least three Guardian employees saw and approved of the image before it was published according to a column by Guardian readers’ editor Elisabeth Ribbans also revealed.

The opinion desk staff did not know Sharp was Jewish and were unaware of the antisemitic connotations of depicting him holding a squid.

Viner wrote: "I was working in the US when this happened, and as soon as I saw the cartoon on Saturday morning I decided with senior editors that we should remove it from our website and publish an apology.

“I know many colleagues were as shocked and upset as I was by the cartoon — there is no place for this type of image in the Guardian…

“The publication of this cartoon highlights failures in our editorial processes which we are determined to address. 

“I am working with some of the senior editorial team on what those changes might be so that we can be sure that something like this won't happen again. Kath.”

The drawing’s problems, she added, were well explained by a piece subsequently written for the Guardian by Community Security Trust head of policy Dave Rich.

“The swift withdrawal of the cartoon and apology by both Rowson and the Guardian are welcome, but really, this should not still be happening,” he wrote for the paper on Monday.

“The Labour party went through years of pain because too many people within its ranks, and in its leadership, either could not recognise antisemitic ideas or actively indulged them.”

Viner also requested that staff read the column published on Wednesday by Ribbans that said the cartoon “should never have been published”.

“I have discussed the cartoon with Rowson and believe he did not mean to conjure antisemitic motifs, but the effect of his depiction of Sharp, alongside references to banking and the tentacles of the squid, inevitably recalled ghastly classic tropes of Jews holding money and power; and in particular the Nazi-era propaganda images of Jewish bankers,” she wrote.

“Including a pig in the context added to the offence, and it is no wonder readers complained forcefully.”

Some readers, Ribbans said, thought other “dangerous tropes” were also visible in the cartoon.

“Sunak was taken to be Sharp’s puppet, and the yellow suckers on the squid’s tentacles seen as gold coins. 

“I believe these are misreadings, likely to have been caused by other suspicious cues and what Rowson called “stupid ambiguities”, which also included colouring red the “Dignity Shreds” the pig was eating, so they were mistaken for blood, and leaving “Gold Sac” on show when it had no meaning.”

Hugh Muir, the Guardian’s executive editor for opinion, who is responsible for the political cartoon, said it should not have been published, she said.

He reportedly told Ribbans: “I feel for all those who were distressed and all those who expect better of us.

“Editors and production staff routinely seek revision of cartoons when we fear they cross the line from lampooning public figures to causing unjustifiable offence.”

“At least” three opinion desk staff saw the cartoon before it went to print, he said, without realising its antisemitic undertones.

Because of this the drawing went to press “with images that would have been harsh in other circumstances but were disastrous when viewed in light of all the facts. This was an undoubted failing, and there will need to be learning from it,” Muir added.

Viner is set to meet Jewish communal representatives in the near future to discuss the cartoon.

On Sunday, the Board said they had written to the Guardian requesting an "urgent meeting" with Viner to discuss the cartoon. 

"This is far from the first time that the paper has crossed the line in terms of highly questionable content connected to the Jewish community,” their statement added.

An apology from Rowson published on Sunday said: “So by any definition, most of all my own, the cartoon was a failure and on many levels: I offended the wrong people, Sharp wasn’t the main target of the satire, I rushed at something without allowing enough time to consider things with the depth and care they require, and thereby letting slip in stupid ambiguities that have ended up appearing to be something I never intended.”