Shah, who was named in the ICC’s Test Team of the Year for 2015, returned a positive result for banned substance Chlortalidone following the second one-day international against England in Abu Dhabi last month.

The 29-year-old, who has 76 Test wickets to his name at an average of 24.17, was suspended by the ICC on December 27 and will be unable to compete until world cricket’s governing body has completed its disciplinary process.

He could be banned for a maximum of two years if found guilty by the ICC.

“Yasir's wife coincidentally is a blood pressure patient and he mistakenly used her tablet without knowing that it contained a banned substance,” PCB chairman Shahryar Khan told cricket.com.au.

“We are confident that he didn't do it intentionally.

“He is a very naive guy and took that medicine out of ignorance.

“Yasir's family has high blood pressure problem and his uncles have suffered strokes and heart attacks due to it.

“He gets similar fears so whenever he suffers from high blood pressure he takes some tablets.”

The PCB, however, seem resigned to the fact that Shah will receive a ban and their appeal seems to be focused on getting the bowler a more lenient punishment.

A statement from the organisation also confirmed they would not ask for a ‘B’ sample test.

“The initial details we received regarding the medicine he had taken were incomplete,” the statement read.

“Now we have received the full details and our doctors have decided against asking for a sample B test.

“We are instead preparing to file an appeal on behalf of Yasir and expecting a lenient punishment as he used the medicine without any wrong intention.”

The news comes amid difficult times for cricket in Pakistan as the return of fast bowler Mohammad Amir, one of three men who were jailed for their part in a spot-fixing scandal where no-balls were deliberately bowled against England in 2010, has caused controversy within the squad.

One-day captain Azhar Ali and batsman Mohammad Hafeez boycotted a recent training camp in protest at his inclusion.

The pair then went back on their original stance but Ali offered his resignation as captain, which was turned down by the PCB.

The other two players involved in the spot-fixing scandal, former captain Salman Butt and fast bowler Mohammad Asif, have also recently made their comebacks for Water and Power Development Authority in Pakistan's domestic one-day tournament.

Pakistan head coach Waqar Younis has refused to rule out their return to the international stage, admitting they would be selected if their form justified their inclusion.

“It's a sort of rebirth for me,” Butt said.

“I will do my best to perform and return to the Pakistan team.”