Ahmed, 29, who was reported for a third time in the West Indies in May this year, will not be allowed to feature in Pakistan's home series against England starting in October unless he is cleared within the next three months.
"The report is highly unexpected for me. I am badly hurt but I have the confidence that I can improve my bowling action," Ahmed said on Friday.
The Pakistan Cricket Board (PCB) had said on Thursday that a biomechanics expert appointed by the International Cricket Council (ICC) had ajudged that Ahmed's action was still suspect.
"The tests Ahmed underwent prove that his bowling action is beyond the tolerance limits of 15 degrees allowed at international level," Board director of operations Salim Altaf said, adding that Pakistan would seek a second opinion.
"Ahmed is an asset for us and we will fight his case. The two options available to us are that we can have a second opinion on his action or we can go to the bowling action review group to contest his case," he said.
Ahmed was first reported in a tri-series competition in Canada in 1998, but was cleared after undergoing some corrective measures by former West Indian bowler Michael Holding.
His action went under the scanner for a second time when he was reported during Pakistan's Test series in New Zealand last year.
Pakistan has been badly hit by illegal bowling action problems, with Shoaib Akhtar, Shoaib Malik, Shahid Afridi and Mohammad Hafiz all having been reported for suspect actions in the past.
According to new ICC rules brought in during March, all bowlers are allowed to straighten their arms to 15 degrees.
Once a bowler's action is reported for being suspect, an ICC-appointed expert analyses the action and if it still exceeds the limit the bowler is immediately suspended.
Any bowler reported twice within two years must be banned for at least a year, according to ICC rules.