"They (the PCB) have challenged the integrity of Akhtar by having a medical inquiry even though Akhtar's medical reports confirmed he was injured," said Khan, a veteran of 82 Tests and 175 One-day games for Pakistan who is now following a career in politics.
"Had I been in place of Akhtar I would have sued the PCB for defamation," he said.
PCB had set up a medical commission to probe whether Akhtar feigned an injury during the third and final Test against India at Rawalpindi last month.
Akhtar fell in his follow-through and did not take field on the third day of the crucial Test but batted without any sign of discomfort on the following day, raising suspicions about his injury.
The home team lost the Test by an innings and handed India their first ever Test series win in Pakistan on their first tour across the border for 15 years.
PCB said medical reports were inconclusive but let off Akhtar with a warning earlier this month.
Akhtar, who is currently playing for Durham County in England, had another scans in England which proved he is still injured.
"How can Akhtar play under the same management who questioned his integrity," asked Khan, leader of the Tehreek-i-Insaf (justice movement) party.
Akhtar had said after the inquiry this month that he was "disappointed" about the probe.
"I am disappointed because my conduct has never been wanting" he said.
"I have always played for Pakistan and can never think of letting down my country."
PCB chairman Shaharyar Khan has said the medical commission report was inconclusive, but the Board decided not to invoke a penalty.