Bottom-of-the-table Tigers decided not to offer Chambers, 30, a contract after he completed a month-long trial at the Jungle which culminated in a Reserve team appearance on the wing against York City Knights nine days ago.

Cas insist they have taken the decision reluctantly and say they have not got the time to work on turning the former World bronze medallist into a top grade player.

Tigers CEO Richard Wright said: "Many people watched Dwain in the trial game and he has certainly won over some of the doubters and proved that the trial was more than simply a publicity stunt.

"During his trial period Dwain has been a joy to have around. His work ethic and professionalism have been exemplary.

"He has got on well with all members of the club's staff that he has come into contact with and he has been in great demand, proving a popular visitor to local schools.

"He has also given us a huge media profile. I believe that he feels that he has gained from his time with us, so there are no losers.

"However our coaching team feels that he would need a significant amount of additional time to prove whether or not he would be capable of making the grade in Super League, and time is something that we don't have.

"All the club wish Dwain the very best for the future in whatever path he chooses to follow."

Speaking on behalf of Chambers, his manager Nick Collins said: "While disappointed, Dwain is comfortable with and understands the decision.

"He has had a great time and made some good friends during his brief period with the club. He leaves the club in a positive mood and with a smile on his face."

It is the latest twist in the career of the London-born sprinter who had been keen to earn a deal with Cas worth a reported £60,000.

In October 2003, Chambers was revealed to have tested positive for the banned anabolic steroid THG. He was given a two-year ban from athletics by UK Athletics in February 2004, backdated to August 2003.

He was also banned for life from the Olympics and stripped of the medals he had won since 2002 after admitting that he had taken THG from that date.

The IAAF has also asked him to return the prize-money, believed to be over £100,000 he won during this period, but he is still hopeful of overturning the Olympic ban.