The BBC has admitted that its promotion of U2's latest album No Line on the Horizon was "inappropriate" and a breach of its guidelines.
The coverage of U2's album launch, which included a concert on the roof of BBC Broadcasting House, was criticised for giving the band millions of pounds' worth of free publicity across TV, radio and online.
The use of the mathematical symbol for identity in the graphic "U2 = BBC" was said to have given an "undue prominence for commercial products or organisations", the corporation's editorial complaints unit (ECU) ruled.
It added that a reference to the BBC being "part of launching this new album" - in an interview between Zane Lowe and U2's Bono on BBC Radio 1 - was "inappropriate".
The alleged "blanket coverage" of U2 across BBC television and radio last February, provoked much criticism from other parties and led to RadioCentre, the commercial radio trade body, making a formal complaint.
The British Conservative MP Nigel Evans said it was the sort of publicity "money can't buy" and he asked: "Why should licence fee-payers shoulder the cost of U2's publicity?"
The BBC ruling added: "In addition, 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.
"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. A session on working with third parties will be included in marketing, communication and audiences monthly editorial issues training programme."
The unit also upheld a complaint from the RadioCentre about the BBC's coverage of a tour by Coldplay. The "Radio 1 presents Coldplay" website included a link to the websites of ticket agents, which the unit said was "not in keeping with the BBC's guidelines on links to external websites".
Radio 1 were also criticised earlier this week by the ECU for an interview with senior BNP members, who said footballer Ashley Cole was ''not ethnically British''.
The interview, broadcast in October last year, was criticised for failing to sufficiently challenge the men on their views on ethnicity.