The former Archbishop of Canterbury, Dr Rowan Williams, has suggested that the World Council of Churches (WCC) could be justified in expelling the Russian Orthodox Church over its failure to condemn the war in Ukraine.
Dr Williams told BBC Radio 4 on Sunday that he was "still waiting" for senior leaders in the Russian Orthodox Church "to say that the slaughter of the innocent in war is condemned unequivocally by all forms of Christianity".
He also had a strongly worded message for Russian Orthodox Patriarch Kirill: "Your own flock are being killed in Ukraine, by other members of your own flock.
"It is your responsibility to condemn the killing of your own flock, for who you are answering to Jesus Christ."
The former Archbishop of Canterbury said that as a "minimum", the Russian Orthodox Church should call for "an effective and credible" ceasefire.
He said he suspected that such a call would have the support of "at least some" Orthodox churches because "I know that there are many people in the Orthodox world who feel that orthodoxy itself is compromised by this, who feel almost ashamed to be associated and I would want to listen very carefully to what other Orthodox churches have to say".
Last month, a group of Russian Orthodox priests started a petition calling for an immediate ceasefire and condemning the suppression of peaceful anti-war protests in Russia.
Turning to the WCC, Dr Williams suggested there was a "strong case" for expulsion.
"When churches are actively supporting the war of aggression, failing to condemn nakedly obvious breaches in any kind of ethical conduct in wartime," he said.
"Then other churches do have the right to raise the question."
"I think there is a strong case for expulsion, because we have seen those signs."
The same suggestion was made last month by Rev Rob Schenck, president of the Dietrich Bonhoeffer Institute in Washington DC.
"Given Patriarch Kirill's aiding and abetting of war crimes perpetrated by Russian forces in Ukraine, the World Council of Churches must act with moral courage, ethical responsibility and spiritual integrity and remove the Moscow Patriarchate of the Russian Orthodox Church from its membership," he said.