The BBC has admitted its coverage of the launch of U2 album No Line On The Horizon last February gave "undue prominence" to the band.
The broadcaster's own editorial complaints unit ruled that a "U2=BBC" on-screen graphic to mark the launch of the album was "inappropriate".
Critics said the BBC had given U2 "the sort of publicity money can't buy".
The UK’s RadioCentre, the trade body for commercial radio companies, made a formal complaint over the coverage.
The BBC’s Editorial Complaints Unit also said that a reference to the BBC being "part of launching this new album", in an interview between Radio 1 presenter Zane Lowe and U2 singer Bono, was inappropriate.
"The Radio 1 leadership team have reminded executive producers and presenters about the issues to be considered in relation to judgments about undue prominence, and the distinction between the reporting of new artistic work and commercial promotion," it said.
"The management of BBC Marketing, Communication and Audiences (the Division responsible for the U2 = BBC graphic) has reminded all staff of the need to consult the editorial policy team in a timely manner for advice when potentially sensitive issues such as commercial interests are involved."
The BBC was also found to have breached guidelines with its "Radio 1 presents Coldplay" website, which included a link to ticket agents for the band's tour.