Tish Seaborne, managing director of the supply company Time-Plan, said that schools throughout the country were starting the year with unfilled vacancies. Her agency had 1,000 on its books alone, 640 of which were in London.
Ms Seaborne praised the London borough of Croydon, which joined forces with TimePlan to send headteachers to Australia to recruit teachers willing to commit themselves to its schools for a year.
The action means Croydon schools have managed to fill their vacancies for this year.
Twenty-three Australian recruits arrived to a mayoral reception in the south London suburb last week. A further 30 are expected to follow in January.
Nearby Grenwich, south-east London, has also recruited 20 teachers from Canada this year, in partnership with TimePlan.
But Ms Seaborne said that boroughs which had not adopted such drastic measures could be in trouble.
Louisa Woodley, Croydon's education spokeswoman, said: "Without our scheme, schools would be in the situation of having to use supply teachers to fill these vacancies more or less on a week-to-week basis.
"They would also find it extremely difficult to recruit subject specialists."
As it is, all of Croydon's antipodean recruits have signed supply contracts with TimePlan to stay a minimum of three terms.
After this, governing bodies have the option of hiring them on a permanent basis, subject to their undergoing training to gain British qualified-teacher status.