Martin Amis has described Jeremy Corbyn as “undereducated”, “incurious” and “humourless” in a scathing condemnation of the new Labour leader.

Writing for the Sunday Times yesterday, Amis said that Corbyn, who won the Labour leadership race last month, was the “fluky beneficiary of a drastic elevation”. Highlighting the politician’s two E-grade A-levels, Amis called him “undereducated”, adding: “In general, his intellectual CV gives an impression of slow-minded rigidity; and he seems essentially incurious about anything beyond his immediate sphere.”

Supporters were quick to leap to Corbyn’s defence on social media, pointing out that neither Winston Churchill nor Nye Bevan, who presided over the birth of the welfare state, had excelled at school.

Amis, the son of the novelist Kingsley Amis, went to Oxford University, where he graduated with a first-class degree in English Literature.

Corbyn’s views, according to Amis, are “pallidly third-hand”, and he “is without the slightest grasp of the national character – an abysmal deficit for any politician, let alone a torchbearer”. The leftwing novelist highlighted Corbyn’s proposal to scrap the army, made in 2012, which would be “a veritable spear through the British soul”, he writes.

The Labour leader is also “humourless”, said Amis – something highlighted by journalists “in a tone of wry indulgence”, but which is actually “an extremely grave accusation, imputing as it does a want of elementary nous”.

Although the novelist allowed that while Corbyn possesses the “demerits – the encysted dogmas – of the old left”, he also “gawkily embodies one of its noblest themes: the search for something a bit better than what exists today: more equal, more gentle, more just”, he failed to see a rosy future for the Labour party under his leadership.

Amis predicted that under Corbyn, the Labour party would devolve “into a leftist equivalent of the American GOP: hopelessly retrograde, self-absorbed, self-pitying and self-righteous, quite unembarrassed by it (years-long) tantrum, necessarily and increasingly hostile to democracy, and in any sane view undeserving of a single vote”.

Former Labour MP for Derby North, Chris Williamson, tweeting: “Martin Amis would do well to remember that Nye Bevan left school at 13 and went on to create the NHS,” while the comedian David Schneider tweeted: “Martin Amis is right. Corbyn’s bad exam results rule him out as PM. Like that other failure at school: Churchill. Thank God he was never PM.” The poet Michael Rosen, meanwhile, tweeted: “Hoping that Labour listen to Martin Amis and make an Oxbridge degree a necessary qualification for leadership of Labour. #GreatIdeas.”

The author of novels including London Fields, Money, and most recently The Zone of Interest, Amis has never shied away from controversy, calling the Royal family “philistines” in an interview with a French magazine and saying that he “would prefer not to be English”. He also engaged in a lengthy and public row with the academic Terry Eagleton about Islam, after he said in an interview: “There’s a definite urge – don’t you have it? – to say, ‘The Muslim community will have to suffer until it gets its house in order.’”