ICC general manager Dave Richardson said fresh 'chucking' laws introduced last year had scientific backing and recognised the fact that almost all bowlers were likely to straighten their arms to some extent during delivery.
The ICC was responding to criticism by former New Zealand captain Martin Crowe, who this week called for "zero tolerance" on chucking, which he dubbed 'cricket's Achilles heel'.
Master Sri Lanka off spinner Muttiah Muralitharan, Pakistan strike bowler Shoaib Akhtar and India's Harbhajan Singh have all come under scrutiny over suspect actions.
The ICC introduced a new threshold in 2005 which allows bowlers to straighten their arms up to 15 degrees. Until then, spinners were permitted to straighten their arms by only five degrees, medium pacers 7.5 degrees and fast bowlers by 10.
Crowe made his remarks on Tuesday while delivering the annual Colin Cowdrey lecture at Lord's.
"I just want to say ... that I have zero tolerance
"I don't care about talk of 15 degrees here or 10 degrees there ... if with the naked eye a bowler is clearly chucking -- even by one degree -- he should be chucked out.
"To straighten your arm from any bent position is a massive advantage over other bowlers who bowl properly ... this is cricket's Achilles heel."
The ICC said experts felt 15 degrees was the point after which the bend is likely to become visible to the naked eye.
"The facts are that some bowlers, even those never suspected of having flawed actions, were found likely to be straightening their arms by 11 or 12 degrees," Richardson said. "And at the same time, some bowlers that may appear to be throwing may be hyper-extending, or bowl with permanantly bent elbows.
"Under a strict interpretation of the law they were breaking the rules but if we ruled out every bowler that did that then there would be no bowlers left.
"The game needed to deal with that reality and the current regulations do just that."
