The BBC news show showed a clip from the second instalment of the Danny Boyle film, T2 Trainspotting, which used the word ‘f******’.
The media watchdog said: “This programme broke broadcasting rules after it aired a clip from an upcoming film, which included offensive language at a time when children were likely to be watching.”
The BBC did acknowledge it had been a “clear mistake” following the incident.
Celebrity Big Brother is in the clear after the regulator assessed complaints into bullying and also a task that saw housemates pretend to snort cocaine, but ruled it will not investigate the show further.
Ofcom received a total of 36 complaints about the behaviour of Nicola McLean towards cleaning guru Kim Woodburn during their time in the house and 15 about the task.
An Ofcom spokesperson said: “We received a number of complaints about the recent series of Celebrity Big Brother.
“We are satisfied that Channel 5 broadcast clear and appropriate warnings about potentially offensive content, and intervened appropriately in heated exchanges and situations.
“We also took into account the audience’s expectations of this well-established reality format, and that the series is shown after the watershed at 9pm.”
An interview with Woodburn on ITV’s This Morning also sparked complaints to Ofcom, but the show will not be investigated after the media watchdog confirmed it had “assessed 23 complaints about the presenters’ style when interviewing Celebrity Big Brother contestant Kim Woodburn on her behaviour in the house”.
Ofcom added: “We found the interview was unlikely to have exceeded the audience’s expectations for the programme.”
This Morning host Phillip Schofield clashed with Woodburn while speaking about her time in the Channel 5 show lock-up, and she described him as a “phoney” during their increasingly heated discussion.
He and co-host Holly Willoughby had asked Woodburn how much money she was paid for CBB and why she argued so frequently with her housemates, and Schofield had suggested she could have been “nicer” on the reality TV programme.