The amount of bad language and violence being broadcast to children before the watershed is increasing, media regulator Ofcom has said.
A Jack Dee joke slipped through the net at a Saturday lunchtime
Ofcom has upheld complaints about five programmes, which were originally meant to go out after 9pm but were broadcast earlier with swear words left in.
They included a Jack Dee sketch in The Green Guide to Life on BBC Radio 2.
Ofcom warned that having inadequate checks was a "serious matter and can lead to regulatory action being taken".
In a message to broadcasters, the regulator said there had been an increase in the number of cases involving "unedited or inappropriately edited" material.
"This material often contains unsuitable language or violence," it said. "In such cases, broadcasters frequently explain such failures on scheduling and/or human error."
But TV and radio stations were "under a clear duty to ensure that robust procedures are in place" to avoid breaking the Ofcom code, it added.
In one of the recent cases highlighted in the regulator's latest complaints report, comic Jack Dee was heard swearing on a Saturday lunchtime, after the show had been moved from its original 2230 slot.
The BBC apologised "unreservedly" and admitted the programme, which was made by an independent production company, should have been checked before being broadcast.
In another case, two people complained after an officer on ITV4's Police Patrol: Uncut swore while reprimanding a suspect.
ITV also apologised unreservedly and admitted an uncut version of the programme had been mistakenly scheduled for the 2000 slot.
Ofcom said a similar thing had happened twice before in the past year, and warned ITV about the "repeated occurrence of this type of error".
Build a New Life in the Country was originally made to be shown after the watershed on Five, but was repeated at 2000 on sister station Five Life with strong language.
Five put the problem down to a number of human errors and said it had taken steps to minimise the risk of a repeat of the incident. It offered its sincere apologies to viewers who had been offended.
"Five said this had highlighted a gap in its current compliance systems," Ofcom reported.
Also on Five, gambling film The Last Casino was "edited thoroughly for afternoon transmission", the channel said - but one swearword remained audible and appeared in subtitles.
"Ofcom is concerned that before this incident Five did not have agreed procedures in place with its contracted subtitle supplier to ensure that the most offensive language was automatically omitted before the watershed," the regulator said.
The final programme mentioned in Ofcom's report was the BBC's Blood on the Carpet, repeated at 1400 on 14 April on the Business Channel.
The digital channel apologised and said the person responsible "failed to comprehend the significance of the watershed" - but Ofcom issued a reprimand because the same thing happened with the same programme four months earlier.