On the Live with Myleene weekday show on May 9, Klass welcomed former GMTV presenter Ben Shephard as a guest to discuss the benefits of a healthy breakfast.
However, Ofcom today upheld a viewer complaint that Shephard had made several references to a Nestlé ad campaign he was fronting during the eight-minute segment.
Ofcom said that the "overall effect of the live interview was to promote and endorse Nestlé cereals".
In the interview, Shepard spent six minutes talking about eating a healthy breakfast, in which time he mentioned Nestlé's 'Battle of the Breakfasts' advertising campaign he was fronting; along with the benefits of changing from current breakfast choices to Nestlé cereals, such as Cheerios or Shreddies; and the fact that further information was available on the Nestlé website 'battleofthebreakfasts.co.uk'.
In response to the complaint, Channel 5 said that it did not have any "deliberate motivation or any arranged pre-meditated interest in promoting… [Nestlé] or its range of cereals".
The broadcaster said that the programme makers were aware of Shephard's connection to Nestlé's 'Battle of the Breakfasts' campaign, but claimed that he was told, both verbally and in writing, about not giving "undue prominence" to the brand during the interview.
As Shephard was a presenter with "many years of live television experience", the Live with Myleene production team felt that he would be aware of the need for any product references to be editorially justified, said Channel 5.
But in its ruling today, Ofcom said that there was "insufficient editorial justification" for the several commercial references made by Shephard.
"Ofcom acknowledged [Channel 5's] response that it did not have a 'deliberate motivation or any arranged pre-meditated interest in promoting this brand or its range of cereals'," said Ofcom.
"However, Ofcom considered that the overall effect of the live interview was to promote and endorse Nestlé cereals."
It added: "The cumulative effect of the manner and frequency of these repeated references, including specific references to the benefits of named Nestlé cereals, was that the brand and its products were promoted during the interview, in breach of Rule 9.4 of the Code."
Despite rapping Live with Myleene, Ofcom welcomed Channel 5's efforts to improve its compliance procedures to ensure such a breach does not happen again in future.
Nestlé was the first commercial brand ever to make use of new UK rules on product placement, when one of its coffee machines legitimately appeared on ITV1's This Morning in February 2011 in an estimated £100,000 deal.