The club said late Tuesday English football's governing body had been "determined" to find Suarez guilty and in a strongly worded statement said the 24-year-old Uruguay striker had not received a fair hearing.
"It appears to us that the FA were determined to bring charges against Luis Suarez, even before interviewing him at the beginning of November," the statement said.
"Nothing we have heard in the course of the hearing has changed our view that Luis Suarez is innocent of the charges brought against him and we will provide Luis with whatever support he now needs to clear his name."
The allegations relate to a 1-1 Premier League draw between bitter foes Liverpool and United at Anfield on October 15 after which France defender Evra claimed he had been racially abused "more than 10 times in the game".
Liverpool said they were stunned that such a lengthy ban should be imposed on Suarez - who has been the club's outstanding player this season - as a result solely of Evra's testimony.
"We find it extraordinary that Luis can be found guilty on the word of Patrice Evra alone when no-one else on the field of play - including Evra's own Manchester United teammates and all the match officials - heard the alleged conversation between the two players.
"Luis himself is of a mixed race family background as his grandfather was black… It seems incredible to us that a player of mixed heritage should be accused and found guilty in the way he has based on the evidence presented."
Liverpool will be provided with the full reasons for the ruling, but several British newspapers have reported the case centred around Suarez's use of the word "negro".
It is believed Suarez told the panel this was a descriptive expression and not deemed offensive in his home country.
Suarez, reacting to the decision on Twitter, said: "Today is a very difficult and painful day for both me and my family. Thanks for all the support, I'll keep working!"
Liverpool manager Kenny Dalglish, who has been staunch in his support of Suarez, also took to Twitter to voice his anger at the verdict.
"Very disappointed with today's verdict," Dalglish said. "This is the time when @luis16suarez needs our full support. Let's not let him walk alone. KD." Liverpool cast doubt on Evra's reliability as a witness, saying: "It is also our opinion that the accusation by this particular player was not credible - certainly no more credible than his prior unfounded accusations.
That was a thinly veiled reference to a 2008 scuffle between Evra and ground staff at Chelsea, when a subsequent FA hearing branded the defender's testimony "exaggerated and unreliable."
Suarez, signed for £23 million ($36 million) from Dutch side Ajax in January, has scored eight goals in 19 Liverpool appearances so far this season.
The Merseysiders statement means they are certain to challenge the ban, and given Suarez remains free to play while an appeal is in progress, he could feature in Wednesday's match away to Wigan.
Liverpool, who saw Premier League champions United surpass their record of 18 English titles last season, are currently sixth in the table, 10 points behind their second-placed north-west rivals.
Suarez's ban could yet have a knock-on effect for England captain John Terry.
British prosecutors are currently considering if there is enough evidence to bring criminal charges against the Chelsea centre-back regarding claims he racially abused Queens Park Rangers' Anton Ferdinand in a Premier League match in October.
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