English teachers who went to school when grammar was not on the curriculum struggle to teach it, research shows.
A review of international studies on the effective teaching of complex writing says there is a need to improve the teachers' own skills.
The work was done by Exeter University for the Department for Children, Schools and Families in England.
The department said its professional standards demanded that teachers have a secure knowledge of their subject.
The study concludes: "For English teachers, who themselves attended schools when grammar was not part of the English curriculum, there is a significant issue of lack of assurance in grammatical subject knowledge, leading to difficulties in addressing grammar meaningfully in the writing classroom.
"In particular, effective teaching requires a secure understanding not simply of grammatical terminology, but of applied linguistics and an awareness of the ways in which grammatical constructions are used in different texts for different communicative purposes."
Among the studies that were examined, a recent one investigated the difficulties faced by trainee teachers when they taught writing.
Being new to teaching, they were trying to understand the processes involved in becoming a writer.
But they were also having to focus on different kinds of writing as a way to meet objectives laid down in curriculum documents.
So they tended to see writing as a process of acquiring discrete skills, such as "writing descriptions" or "using complex sentences".
They tended to get bogged down in the mechanics and neglected the writers' ideas or engagement with the reader.
Another study described a "significant knowledge gap" in terms of teachers' pedagogical knowledge.
One piece of research on the linguistic subject knowledge that teachers and trainee teachers bring to their teaching of writing found "a persistent theme in teachers' attitudes to grammar is hostility to anything that makes formal structure the central object of study".
This claimed few teachers brought any specialist knowledge of grammar to their training from their degree studies but did bring "many anxieties and misconceptions around 'grammar'."
'Lack of confidence'
It added that "it is the height of folly to send them into schools where they will have to teach grammar without making time during their training for them to get to grips with the subject".
A study of the linguistic subject knowledge of trainee teachers in the UK found that two thirds reported a lack of confidence about grammar.
"They felt that their greatest need was in using grammar to support EAL [English as an additional language] and knowing when and how to teach it.
"Trainees reported that they embarked on topics and then stumbled into difficulties. Even simple topics seemed to become complex."
A spokeswoman for the schools department said: "We know that grammar is important and that is why it is a compulsory part of the national curriculum.
"In particular, primary teachers focus heavily on sentence construction, grammar and syntax as part of teaching reading and writing, for which there are specific national curriculum targets.
"Our professional standards for teachers demand that they must have a secure knowledge of their subjects and curriculum areas to enable them to teach effectively across the age range they trained for. And Ofsted has said that we have the best trained teachers ever."
Effective Ways of Teaching Complex Expression in Writing - a Literature Review of Evidence from the Secondary School Phase by Debra Myhill, Ros Fisher, Susan Jones, Helen Lines and Alun Hicks, University of Exeter