Recruitment to primary courses is generally buoyant, according to training providers. Yet London heads say one in 10 primary posts is unfilled, or covered by overseas-trained or unqualified teachers.

“The problem is that primary supply to London is inadequate . So it has to rely heavily on overseas and newly-qualified teachers,” said one university’s head of education.

“We could grow. But not only is the Teacher Training Agency not giving us enough places, the unit of funding is chronically inadequate.”

The TTA is funding more than 1,400 additional primary training places this year, and the number of students accepted on to courses was up 17.5 per cent on last year, according to recent figures. But only 204 of the extra places are in London, despite the capital’s continuing recruitment crisis.

By law, the agency has to take into account the quality of provision when allocating training places, and it has usually offered additional places only to the top A or B-graded providers.

Some have argued that this has weighed against extra places being given to London, which last year had a mixture of B and C primary provision and two failing courses.

The TTA is now considering offering more places to institutions considered merely satisfactory, to ensure enough new teachers enter the system. It may also give failing institutions more time to recover before penalising them.

Mary Russell, secretary of the Universities Council for the Education of Teachers, said funding was at crisis point: “The business of the Government thinking that all you have to do is increase target numbers has always been daft.”

Ministers acknowledged the funding problem by agreeing earlier this term to bail out London University’s Institute of Education, to the tune of pound;1 million a year for the next three years.

The institute, which trains more than 1,000 teachers a year, had threatened to pull out of initial training because of the gap between funding and spending on postgraduate courses.

Other providers point to problems with finding enough good-quality school placements for more trainees, and highlight retention issues - both on their courses, and in schools once students qualify.

Lawry Price, deputy head of the school of initial teacher training at University of Surrey Roehampton, said: “Most of our students will tend to stay in London or nearby for the first year or two. It is a good training ground.

“You can’t blame teachers for then wanting to take those skills to other areas where it costs less to live or you get more for your money.”