Latest figures suggest there are just two applicants for each place on primary undergraduate courses, prompting fears over the quality of future students.
And despite the increase in postgraduate applications - the usual route into secondary teaching - many courses still have vacancies and some shortage subjects will not hit targets, according to recruitment experts.
Applications to one-year secondary courses are up a quarter on last year to 17,793 in England and Wales, according to the Graduate Teacher Training Registry. Primary applications are up a fifth to 14,488.
However, applications to UK undergraduate primary courses were down 11.5 per cent to 52,805 as of May 16. With each candidate making around five applications and around 6,070 places available on primary degree courses, that equates to around two cadidates per place. A few years ago, the figure was nearer three.
Teacher training institutions fear recruitment initiatives targeting the postgraduate route, such as pound;6,000 training bursaries and the waiving of tuition fees, have discouraged students who might otherwise have chosen the degree course.
Mary Russell, secretary of the Universities Council for the Education of Teachers, said: "There is concern that if we have too few applying then we don't have the breadth of choice to make sure we just take in the best."
Recruitment analyst John Howson said many secondary postgraduate courses still had vacancies, even in popular subjects such as English, where 65 of 90 courses have unfilled places. In maths, 97 of 99 courses have spaces, and the subject is unlikely to recruit to target despite an 18 per cent increase in applications, he said.
The Government wants to recruit 12,500 primary and 17,390 secondary teacher trainees in England for 200102.