The blunder was not realised by the news channel until they watched the footage.
The raunchy video of a naked blonde woman appeared on the channel as it debated on Ed Miliband's leadership of the Labour Party.
The video clip is believed to be from an episode Shameless of Channel 4 drama. The woman appeared on the channel for few seconds as John MacKay, the host of the show interviewed Dan Hodges, a political blogger.
Reports reveal that Hodges was in ITNs London studio, when the woman appeared on a screen behind him on Jan 20. The channel, however, apologised for the mistake after Paul Traynor, a viewer made a formal complaint.
The channel's spokesman said that STV hoped that the viewers were not too distracted with the incidental content that flashed across on the show.