Melbourne, Jan. 26 : Controversy surfaced at the Australian Open here on Sunday when tennis player Tomas Berdych questioned the accuracy of the Hawk-Eye electronic line-calling system at a vital stage of his quarter-final match against defending champion Roger Federer.

The system which simulates ball flight to determine close calls was unable to offer an opinion on a line call, leading to an angry Berdych questioning the chair umpire over the apparent failure of the system to show a simulation of a ball called out early in the fourth set, reports The Australian.

He was told that officials had ruled the original call of "out" would be upheld.

"I don''t care about officials, I just want to see my ball," he told the umpire.

The Hawk-Eye simulator is believed to have failed to make the call due to the heavy shadow over the line in question.

The incident raises doubts over the efficiency of a system that can be affected by such vagaries, but is still called on to make decisions which come down to a matter of millimetres.

Federer, a long-time opponent of the system, said the incident had only confirmed his doubts.

"I think it''s horrible," he said.

Berdych became a convert to the anti Hawk-Eye push, saying it shouldn''t be used if it isn''t perfect.

"Why it should be on the courts if it isn''t working. It should be working all the time," he said.

The International Tennis Federation said Hawk-Eye met their margin-of-error parameters which were 5mm either way.

In the face of earlier questions on the accuracy of the system, Hawk-Eye''s developer Dr Paul Hawkins said it had been extensively tested and was yet to have been shown to make a mistake.

"It has undergone thousands of tests and it got every one right. ITF decided that 5mm was an acceptable margin of error and Hawk-Eye''s level of accuracy is well under that," Dr. Hawkins said. (ANI)