Proliferation of tests prompts exam boards to look overseas for suitably qualified assessors.
The government is investigating hiring teachers from around the world to mark national tests as it struggles to find examiners to grade the ever-growing number of assessments.
This year, the Qualifications and Curriculum Authority will conduct the second of a series of trials in which experienced Australian teachers are asked to mark tests to check the accuracy of results.
If the move proves a success, computer technology may later be used to send key stage tests for marking overseas. Exam boards already use staff abroad to "process" mutiple-choice and short answers for GCSE exams. AQA has used staff in India, while Edexcel has marking centres in Australia and the United States.
Colin Watson, head of standards at the QCA, told a London conference that with a host of new tests on the horizon, the need for examiners was likely to become severe.
New "progress tests", in which teachers will be able to enter pupils for tests in English and maths up to twice a year, are to be trialled from this year. Diplomas are also to be introduced, incorporating new functional skills tests in English, maths and science, from next year. This means finding good-quality markers will be a challenge.
Mr Watson told the Institute of Educational Assessors' conference that the new qualification would exacerbate the difficulties that already exist in finding enough key stage 3 markers.
"We are going to run out of sufficiently qualified markers, and if we do not want to just take anyone, we are going to have to look elsewhere," he said.
He said one solution might beto use computers to mark tests. But this would be easier in certain subjects, such as maths, than for English.
Last year, a QCA trial in Sydney, Australia, gave 2006 KS3 maths papers to 38 experienced Australian teachers, and compared their results with those of four senior English markers. Both marked very accurately, with the Australians performing as well as the English. This year, the trial will be repeated for KS3 English.
Mr Watson said there were no immediate plans to have those papers marked overseas, partly because key stage test scripts are not yet scanned electronically for marking.
The Australian test had been designed to check the overall reliability of UK markers, rather than the potential for sending the tests overseas.
David Gee, head of the National Assessment Agency, said marker recruitment had gone well this year, with sufficient examiners found for all national tests.