Zurich Premiership champions Wasps have been disqualified from the Powergen Cup by the Rugby Football Union (RFU) for fielding an ineligible player.
Barrett was the unwitting cause of Wasps' disqualification
Hooker Jonny Barrett played in Wasps' sixth-round 43-33 win over Bristol last weekend even though he was cup-tied.
The ruling by the RFU is unprecedented in English rugby and means Bristol will take Wasps' quarter-final place against local rivals Gloucester on 22 January.
Wasps have no plans to appeal against the decision.
"The club has admitted its mistake and needs to take the punishment like all
clubs in this tournament," said Wasps chief executive David Davies.
"At this time of year, with other major games coming up, it was in everyone's
best interest to make a quick decision and allow us to concentrate on the
upcoming fixtures against Gloucester and Biarritz in the Heineken Cup.
"We regret the deep embarrassment this incident causes to the club, our
supporters and its players."
During a loan spell at Henley earlier this season, Barrett took part in the club's third-round defeat at the hands of Moseley on 16 October.
Wasps director of rugby Warren Gatland then fielded the hooker against the Shoguns in contravention of RFU rules.
The mistake, described as "an administrative oversight", came to light after a joint investigation between Wasps and the RFU.
"We have accepted it as a mistake made on the part of the club," said RFU community and operations director Terry Burwell.
"The regulations are very clear, however, and we had no other option but to
enforce them. The penalty will take effect for this season only."
Wasps won English rugby's premier domestic cup competition in 1999 and 2000. But the news they will not be able to advance this time around will further dent their ambitions this season.
Wasps are struggling to maintain their Heineken Cup title defence after back-to-back defeats by Leicester earlier this month in the group stages. And the reigning domestic champions are second behind the Tigers in the Premiership.