Ian Evans will miss Wales' entire RBS 6 Nations campaign after receiving a 12-week ban for stamping.
Ospreys lock Evans was sent off for stamping on Leinster forward Mike McCarthy during a Heineken Cup pool game in Dublin last Friday.
Evans admitted the offence at a disciplinary hearing in Dublin on Thursday, European Rugby Cup announced. He cannot play again until April 21.
And Evans' punishment was accompanied by criticism of his actions from independent judicial officer Jeremy Summers.
In a statement, ERC said: "In upholding the red card decision, the judicial officer stated that the incident involved at least two stamps which connected with McCarthy's head and which resulted in a serious facial wound.
"Mr Summers also stated that there was no place in the game for conduct of this kind - a view which Evans himself accepted during the hearing.
"The judicial officer determined that the offence was at the top end of the IRB (International Rugby Board) sanctions for offences of this nature and selected 16 weeks as the appropriate entry point.
"As there were no aggravating factors, he reduced the suspension by four weeks due to the player's guilty plea, good conduct and remorse during the hearing.
"The period of suspension runs over 13 weeks as the judicial officer chose to take into account one week during the Six Nations period when the player would not have played."
Evans, 29, has won 32 caps and toured Australia with the British and Irish Lions last summer.
He would undoubtedly have been a key part of Gatland's Six Nations plans, having established a strong second-row partnership at regional and Test level with Jones.
Evans, who has the right of appeal, was red-carded in the 20th minute by French referee Romain Poite. Summers heard evidence and submissions at the hearing from Evans, Ospreys team manager Andy Lloyd and ERC's disciplinary officer.
Versatile Ospreys forward James King had already been called up by Gatland as Six Nations cover, while Scarlets second-row prospect Jake Ball has been training with the Wales squad.
Gatland will announce his team to face Italy next Tuesday.
Independent judicial officer Roger Morris heard evidence and submissions from White, who pleaded guilty to the offence, at a hearing on Thursday.
ERC said: "In upholding the citing complaint, the judicial officer determined that the offence was in the mid-range (five weeks) of the IRB sanctions for offences of this nature.
"As there were no aggravating factors, he reduced the suspension by two weeks due to the player's guilty plea, his clean record and good conduct and remorse during the hearing.
"The three-week suspension will run over a five-week term as the judicial officer chose to take into account two weeks during the period when the player would not have played. White is therefore free to play on Monday, 24 February."