Teachers shouldn't dream of lightly tossing aside the guidance from the Department for Education and Skills on how to teach English. It should be thrown with great force, according to three writers asked to review what they evidently found was a dismal document.

The trio - playwright Simon Gray, biographer Selina Hastings and poet Anthony Thwaite - were dismayed by the jargon, bad grammar and clumsy language of the DfES handbook, Framework for Teaching English: Years 7, 8 and 9 (ages 11 to 14).

Asked by RSL, the Royal Society of Literature's magazine, to award the department marks out of 100, Mr Gray and Mr Thwaite gave officials "nul points" - putting it on a par with our dire effort in the Eurovision Song Contest last year.

Mr Gray said he just couldn't understand it. Ms Hastings, who has chronicled the life of Brideshead Revisited author Evelyn Waugh among others, took pity on the DfES and gave it 30%.

RSL showed them extracts such as: "Support is focused in the core subjects of English, mathematics and science together with other language-rich subjects as humanities and R.E. departments have to bid in for support, making clear their commitment to the work and nature of development required."

Mr Thwaite was dismayed by its "bad grammar, pretentious barbarisms and vulgarisms which sound like stuff produced by third-rate advertising copywriters". He demanded: "How can children learn clarity and elegance of expression if their teachers think this is the way to write?"

Ms Hastings branded the guide "an ugly piece of prose" and said the "reliance on jargon is not only unpleasing to the ear but tends to obscure the sense". She added: "The author's own use of English is clumsy and inaccurate."

Mr Gray said: "I have now read it a number of times and find myself unable to mark it as I simply don't understand it. I think one should ask its perpetrators whether they write to their husbands or wives, lovers, children, friends etc in such language. If they don't, one should ask them why not; if they do, then God help us. I can't tell you how dispiriting I find it."

RSL editor Anthony Gardner said the magazine decided to "examine the examiners" after a teacher brought the offending DfES document to one of the lunches organised by the society on the teaching of English in schools.

"I think it may be a case of institutional illiteracy," he said.

A DfES spokeswoman said: "We are committed to excellence and clarity in the use of the English language, and follow the Plain English Campaign guidelines in our public communications. Our national literacy strategy is boosting standards of literacy with international surveys showing that English 10-year-olds are now the third best readers in the world."

The department has not commented publicly on what it thinks of the work of its three critics.