The 31-year-old Wakefield star tested positive for a banned substance in November and after being charged by UK Anti-Doping, on Friday admitted taking human growth hormone.
The Wildcats terminated Newton’s contract with immediate effect yesterday before UKAD announced his ban, which runs up to 23 November 2011.
Newton is one of only five players to have appeared in all 15 seasons of the Super League, but has played just twice for Wakefield since his close-season move from Bradford.
A Wildcats statement read: “Wakefield Trinity Wildcats are fully supportive of the RFL’s principles of a drug-free sport and the club works hard to inform its players through the ‘100 per cent ME’ campaign about the dangers of drugs and consequences of taking drugs, or breaching the anti-doping regulations.”
Newton, who won 15 caps for Great Britain, said on Friday: “I wish to formally apologise to my family, friends, colleagues and staff at Wakefield, the club’s supporters and the game of rugby league.
“I have made a grave error of judgment in taking a banned substance and hope that, if nothing else, my stupidity will be a warning to any other professional of the consequences of doing so.”