Attoub was found to have deliberately made contact with Ferris's eye
Stade Francais's David Attoub has lost his appeal against a 70-week suspension for eye-gouging.
In January, the prop was found guilty of gouging Ulster's Stephen Ferris during a Heineken Cup tie in December.
Attoub, 28, contested the guilty verdict and length of the suspension at an appeal hearing in London on Tuesday.
But the original ruling - the second longest ban in union's history for a gouging offence - has been upheld and he cannot play before 22 April, 2011.
A statement on the European Rugby Cup website read: "The Independent Appeal Committee, chaired by Professor Lorne Crerar (Scotland) and also comprising Rod McKenzie (Scotland) and Robert Williams (Wales) found that Mr Attoub had not demonstrated that the original decision had been in error and therefore dismissed the appeal."
Attoub was deemed to have gouged flanker Ferris during a match in Belfast on 12 December last year.
And when he delivered the original verdict, judicial officer Jeff Blackett said: "This is the worst act of contact with the eyes that I have had to deal with.
"It is a case of deliberate eye-gouging which caused significant distress and some injury to the victim. The sanction must be such to make other players stop and think before someone suffers a really serious eye injury."
Stade's president Max Guazzini accused Blackett of anti-French bias following the ruling, which is second only in length to the ban imposed on Richard Nones in 1999.
The Colomiers prop was handed a two-year suspension for gouging hooker Sven Cronk during a Heineken Cup match against Pontypridd.
Attoub's team-mate Julien Dupuy, meanwhile, is serving a 23-week suspension for another gouging offence in the same match as the Attoub incident.
Dupuy was originally handed a 24-week ban before Christmas - with Ferris again having been on the receiving end - but that suspension was reduced by seven days following an appeal in January.
Ferris told a January disciplinary hearing that the Attoub incident was "much worse that the contact made by Dupuy with his eyes just moments earlier".
Stade finished top of Heineken Cup Pool 4, ahead of second-placed Ulster, and face Toulouse in the quarter-finals on 11 April.