The England elite squad member is suspended until November 1 following an RFU hearing at a Heathrow Airport hotel on Thursday night, English rugby's governing body announced. The ban runs from March 22.
Clark, 22, was cited after an incident during Northampton's LV= Cup final defeat against Leicester 11 days ago, and then suspended indefinitely by his club.
Clark, who captained Saints in the final, was reported for an act contrary to good sportsmanship, allegedly hyperextending Leicester hooker Rob Hawkins' right arm.
It left Hawkins with a broken elbow and requiring surgery, sidelining him for the rest of this season.
In a statement the RFU said: "Calum Clark of Northampton Saints was this evening suspended for 32 weeks for an act contrary to good sportsmanship - Law 10(4) (M).
"Clark pleaded guilty to hyperextending the right arm of Leicester Tigers' Rob Hawkins during the LV= Cup final at Sixways on March 18.
"The suspension will run from March 22 to the November 1. He is free to play again on November 2 2012.
"Clark is ordered to pay hearing costs of £500.
"The full judgement will be made available tomorrow. The player has the right to appeal."
Clark is the second Northampton forward to receive a lengthy ban this week after club skipper and England hooker Dylan Hartley landed an eight-week suspension for biting Ireland flanker Stephen Ferris' finger during an RBS 6 Nations game on March 17.
Hartley will be available for England's three-Test summer tour to South Africa and the Aviva Premiership final at Twickenham on May 26, should play-off contenders Saints get there.
But Clark faces a far longer period of time in which to contemplate his actions that left an opposition player seriously injured.
A former England Under-20 skipper who joined Northampton from Leeds Carnegie, Clark is viewed among a promising array of young back-row talent currently available to newly-appointed England head coach Stuart Lancaster.
But an RFU panel, chaired by the organisation's disciplinary officer Judge Jeff Blackett, left Clark knowing in no uncertain terms how his behaviour in the LV= Cup final has been viewed.
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