Toronto Maple Leafs forward Carter Ashton has been suspended for 20 games for violating the terms of the NHL and NHL Players' Association's drug policy.


Ashton says he unknowingly ingested prohibited substance Clenbuterol through an inhaler used to treat asthma.


Under the terms of the Collective Bargaining Agreement, the suspension is accompanied by mandatory referral to the NHL/NHLPA substance abuse and behavioural health program.


Ashton will forfeit $169,185 U.S. based on his annual salary.


Ashton has played three games for the Maple Leafs this year and has not registered a point.


He has 16 goals and seven assists in 24 games with the American Hockey League's Toronto Marlies.