The Daily Mail has launched its most savage ever editorial attack on long-time critic The Guardian accusing it of “fake news” and being a “purveyor of hatred”.

The excoriating attack appears to be a declaration of all-out war against its left-wing rival. It follows various pieces of Guardian coverage including one which compared the Daily Mail to an “open sewer” and a reader’s letter which said it was an “organ of hate speech”.

Daily Mail editor Paul Dacre appears to have been spurred into action by a Guardian cartoon which depicted the van which attacked mosque worshippers at Finsbury Park with the words: “Read Sun and the Daily Mail” on the side of it.

In a comment piece headed: “Fake news, the fascist Left and the REAL purveyors of hatred” the Mail said: “..this week the Guardian published a cartoon so sick and disgusting – so deranged and offensive to the four million decent, humane and responsible people who read us – that we owe it to every one of them to lay to rest this malicious smear.”

It added: “The Guardian was telling its followers that the Daily Mail and its readers are vicious bigots with the blood of innocent, peace-loving Muslims on their hands.

“If this had been an isolated example of the Left’s bilious malice, we might have let it pass with nothing more than a shudder of revulsion…

“But this is far from a one-off insult to our readers, who – as should go without saying – were as horrified and appalled as the rest of the country by the Finsbury Park attack.”

It noted that earlier this month Guardian online columnist Sophie Heawood tweeted: “Genuinely excited for a future in which the Daily Mail readers are all dead.”

It also singled out Guardian writer Owen Jones who described the Daily Mail as an “open sewer” in March and complained about a Guardian readers’ letter which yesterday described the Mail as “the main organ of hate speech in Britain”.

It said: “For the Guardian’s editor to publish such deluded, defamatory nonsense – which in itself is a naked incitement to violence – speaks volumes about the hatred that drives this ‘voice of liberalism’.”

The Mail said it wouldn’t matter if The Guardian’s “infantile lies” were confined to the pages of a “little-read dying paper”.

“But in this age of social media, they are spread and amplified through the great distorting echo-chamber of the internet, where the mob really does rule…”

It said: “For the record – not that this matters to the fake news the Guardian creates about the Mail – this paper has always been against UKIP, so much so that Nigel Farage blamed as for his lack of electoral success.”

It also noted that Mail was against the wars in Iraq and Libya, was the first paper to condemn Guantanamo Bay and has consistently opposed UK involvement in torture.

The Mail said that its campaign to bring the Stephen Lawrence murderers to justice “did more to improve race relations in this country than anything the Guardian has ever achieved”.

The leader accuses The Guardian of “criminally stupid business decisions” which have lost it hundreds of millions and says “in the name of sanctimony, what, when you handle your own affairs so badly, gives you the right to sit in judgment on other papers?”

And it says: “Your jaded product is addicted to subsidy and steeped in public sector mentality.”

It concludes: “The truth is that the Guardian and the fascist Left are the real purveyors of hate in this country.”

It also notes that Mail Online is a “totally separate entity” from the daily paper with “very different world view”.

Hitting back at a Guardian story that claimed controversial columnist Katie Hopkins wrote for the daily paper, the Daily Mail said: “That was a lie.

“The Guardian and its writer know that Ms Hopkins has nothing to do with the Daily Mail, but works for Mail Online – a totally separate entity that has its own publisher, its own readership, different content and a very different world view.

“The Guardian knows this because the Mail has told it countless times, but, hey, why let a little lie get in the way of a good smear?”

Hopkins was fired from LBC radio after attracting controversy over a comment apparently referencing the Holocaust following the Manchester bombing, which killed 22 people including children, last month.

In a tweet, the day after the attack, she said: “22 dead – number rising. Schofield. Don’t you even dare. Do not be part of the problem. Be part of the solution. We need a final solution. #Manchester.”

Hopkins continues to write for Mail Online, with whom she has a regular column.

The Daily Mail is headed up by editor Paul Dacre (pictured top), while publisher Martin Clarke runs the Mail Online.

Both titles are owned by DMG Media, a subsidy of the Daily Mail and General Trust (DMGT). They are also both based at Northcliffe House on Kensington High Street.

Content from the Daily Mail is uploaded onto the Mail Online website, which also produces its own independent content.

A Guardian spokesperson said: “Guardian journalism is based on principles of quality, trust, integrity and facts.”