Good Morning Britain breached broadcasting rules with an interview featuring TV presenter Judith Chalmers.
The 84-year-old, best known for holiday programme Wish You Were Here...?, was interviewed by Kate Garraway and Ben Shephard.
Ofcom received a complaint that Chalmers promoted Travel Republic with several references to the company in the July broadcast.
Chalmers had been voted the UK's "all-time leading TV travel icon" in research commissioned by Travel Republic.
Her comments included stating that they "sell 300,000 holidays a year" and that "it's a marvellous company".
ITV said host Shephard politely attempted to move the conversation off the topic with his comment "Sounds great".
But Ofcom said the comment had the effect of appearing to confirm, rather than shift focus away from, the favourable references.
The interview breached rules that "products, services and trademarks must not be promoted in programming" and that "no undue prominence may be given in programming to a product, service or trademark".
An Ofcom spokeswoman said: "Our investigation found that an interviewee on this programme made promotional statements about an online travel agent, to which she was commercially linked, without sufficient editorial justification."
ITV have been approached for comment.
