Kremlin-backed broadcaster RT breached impartiality rules with several programmes which aired in the UK after the Skripal poisoning, watchdog Ofcom has said.
The RT news channel, formerly Russia Today, failed to be impartial in seven news and current affairs programmes over a six-week period up to May.
The programmes were mostly about the Skripal poisoning or the conflict in Syria.
Diplomatic relations between the UK and Russian governments have been tense following the poisoning of Russian ex-spy Sergei Skripal and his daughter Yulia in Salisbury, Wiltshire, in March.
Watchdog Ofcom said it was "minded to consider imposing a statutory sanction" on RT.
It said RT failed to give due weight to a wide range of voices on a matter of major political controversy.
Possible penalties could include the broadcaster being fined or even having its licence revoked.
RT's licensee TV-Novosti alleged that Ofcom was under intense pressure from the UK Government, which the watchdog has strongly denied.
RT said they were "extremely disappointed" in Ofcom's conclusions.
RT added: "We operate under rules outlined by the regulator, and always strive to abide by them.
"It appears Ofcom has failed to fully take on-board what we said in response to its investigations and, in particular, has not paid due regard to the rights of a broadcaster and the audience.
"We are reviewing the findings Ofcom has put forward and will decide shortly the nature of our next steps.”
'A Russian perspective'
Military personnel wearing protective suits remove a police car and other vehicles from a public car park in Salisbury in March, 2018.
The broadcasting watchdog launched investigations into RT, earlier this year.
The channel is produced in Russia, "providing a Russian perspective on UK and global news and current affairs related programming", it says.
Theresa May recently warned that politicians appearing on RT risk being used as "propaganda tools".
An Ofcom spokeswoman said the breaches "represent a serious failure of compliance with our broadcasting rules".
She added: "Our investigations found that RT failed to maintain due impartiality in seven news and current affairs programmes over a six-week period.
"Taken together, these breaches represent a serious failure to comply with our broadcasting rules.
"We have told RT that we are minded to consider imposing a statutory sanction for these breaches. The broadcaster now has the opportunity to make representations to us, which we will consider before proceeding further."
Ofcom recently found that an edition of The Alex Salmond Show on the channel breached broadcasting rules for presenting messages as having come from viewers when they were from production staff.