All Scottish news programmes on STV are expected to be cancelled on Wednesday as journalists stage a day of strike action.
Editorial staff are walking out in a dispute over compulsory redundancies and plans to end a separate news service for the north of Scotland.
The National Union of Journalists (NUJ) is planning protests outside STV’s Glasgow headquarters and its Aberdeen offices.
Scottish organiser Nick McGowan-Lowe said members were striking in opposition to compulsory redundancies and a management which he claimed “wanted to rip up” public service broadcasting obligations.
He said: “Viewers, staff, business leaders, politicians and unions all know STV's plans are desperate, shortsighted, damaging to Scottish journalism and in complete disregard of the viewers and communities in the north of Scotland who depend on local coverage from STV News.”
STV said the action was “ill-timed” while consultation with unions was ongoing.
A spokesperson added: “Our proposals will protect our valued news service in the face of a dramatically changing media landscape.”
Ofcom’s consultation on the proposed changes runs until February.