Pakistan fast bowler Mohammad Asif [Images] is challenging his positive test result for a banned substance during this year's Twenty20 Indian Premier League [Images] (IPL) and is requesting a "B" sample test.

• Special: Cricket's hall of shame

"My lawyer is now handling the issue and I am not allowed to speak but I will do everything to prove my innocence. We will ask for a "B" sample test," he told reporters on Tuesday, a day after the IPL revealed the bowler had tested positive.

Under World Anti-Doping Agency (WADA) regulations, an athlete who has tested positive for a banned substance in a preliminary test can appeal for a second test of his sample.

• No WADA rule violated: BCCI

"My client is a victim and he is innocent. He has no idea how his test came positive when he has not taken any drugs or banned substances," Asif's lawyer Shahid Karim said.

Asif, who has played 11 tests and 31 one-day internationals, has been involved in a series of doping scandals since 2006.

Two years ago, he tested positive for nandrolone during out-of-competition tests carried out by the Pakistan Cricket Board and last month spent 19-days in detention in Dubai for alleged possession of a banned substance.

"My client has represented his country with pride and honour and he is keen to play for his country again. He is confident he will be cleared and he will stand vindicated that he is innocent of drug use," Karim said.