ICC General Manager-Cricket, David Richardson, explained that Shabbir's action could only be reassessed at the end of his one year suspension, which was imposed on the 29-year-old after being reported during the first Test against England in Multan in November last year.
"We have in place a process that was supported by all of our Full Member countries which states that if a player is independently assessed to have been bowling with an illegal action twice in two years they will be suspended from bowling in international cricket for one year," said Richardson, a former South African wicketkeeper.
"If a player does not accept the independent assessment of his action then he can request a hearing of the Bowling Review Group (BRG).
"In Shabbir's case the BRG upheld the findings of the independent assessment which means that, unfortunately for him, he will not be able to submit for reassessment until December 2006.
"This suspension provides Shabbir with an opportunity to address the concerns that have been raised by the independent assessments.
"The 12 month time period is set to ensure that a bowler can modify his action not merely to pass a test but to embed improvements on a permanent basis so they will withstand the demands of bowling long spells under the pressure of international cricket."
Ahmed, who has taken 51 wickets in 10 tests, is the first bowler to be banned for 12 months.
Ahmed was banned after tests on his bowling action proved he exceeded the prescribed limit of 15 degrees for a bent arm on the delivery stride.
He underwent remedial measures on his action supervised by former Pakistan seamer Sarfaraz Nawas, but the ICC's review group upheld the suspension.
The review group included former Indian paceman Javagal Srinath and Sri Lankan batsman Roshan Mahanama.