A competition designed to enable schoolchildren to meet pop band McFly has led to the BBC being rapped by the communications watchdog.
As part of last year's Comic Relief, regional programme North West Tonight offered viewers a free competition to win a visit from McFly to a school anywhere in the north-west region.
However, after it emerged that the band would only be able to make a trip to a school in the Greater Manchester area, the broadcaster failed to change or cancel the competition meaning that many of the entrants were not able to win the prize.
As part of an Ofcom investigation, the BBC admitted that the contest was "unfair" and "apologised unreservedly for its mistake".
But the broadcaster pointed out that at the competition's conception it was fair and said it was only made aware of the problem on the final day of the contest.
"All entries were solicited in good faith and the programme-maker's original understanding was that the group was prepared to visit any of the primary schools in the North West Tonight region," the BBC told Ofcom.
In making its decision, the regulator said it had taken into account there had been "limited harm to viewers as entry was free by way of email and that a genuine local school won the prize".
But it criticised the BBC for not pulling the prize draw once it knew that the original expectation of the contest could not be fulfilled.
"Ofcom underlines to broadcasters that if a material problem arises with the conduct of a competition, viewers or listeners must be informed as soon as possible," the watchdog said in a statement.
"Broadcasters must not proceed with the competition without informing the audience of that problem if it is likely to affect viewers or listeners' decision to participate."
North West Tonight publicised the contest between February 6th and 8th last year, with the school visit taking place a day after it closed.