Liberal Democrat David Ward will be hauled before Nick Clegg to face disciplinary action over comments about “the Jews”.
The Bradford East MP was summoned to meet chief whip Alistair Carmichael on Monday night, but must now defend his actions to the party leader.
Lib Dems said there would be “further meetings”, but would not say whether Mr Ward could be kicked out of the party.
The row blew up over a posting made by Mr Ward after signing a memorial book to mark Holocaust Memorial Day last month.
He wrote that he was “saddened that the Jews, who suffered unbelievable levels of persecution during the Holocaust, could within a few years of liberation from the death camps be inflicting atrocities on Palestinians and continue to do so daily”.