Labour has made a "veiled attempt to silence" a Jewish MP after a confrontation with Jeremy Corbyn over anti-Semitism, lawyers have suggested.
Law firm Mishcon de Reya questioned the "fairness and legitimacy" of a disciplinary investigation launched into Dame Margaret Hodge after a spat with the Labour leader and said the party had failed to set out what she is accused of.
It comes as Mr Corbyn faces fresh pressure from Labour's MPs and peers over the party's policy on dealing with prejudice against Jews.
The Parliamentary Labour Party is set to debate an emergency call to adopt the International Holocaust Remembrance Alliance's (IHRA) full definition of anti-Semitism.
Labour launched an investigation into Dame Margaret after she confronted Mr Corbyn in the Commons about problems tackling anti-Jewish sentiment in the party.
The MP was reported to have called him a "f****** anti-Semite and a racist", but in the legal letter she denied having sworn at the party leader.
"This is vehemently denied, and our client is aware of multiple witnesses who can testify that she did not swear," the letter states.
"Any allegation that our client was abusive is false."
Dame Margaret, who lost family members in the Holocaust, again stood by her actions in confronting Mr Corbyn, however, saying the current row had been a "bridge too far".
In a letter to Labour's general secretary, Jennie Formby, Mishcon de Reya said, given the party had failed to explain the allegation against the MP or the rule that it has breached, "your threat to suspend our client if she repeats this non-particularised conduct appears to be a veiled attempt to silence her".
It added: "Again, it is a fundamental breach of natural justice and principles of fairness. You have left our client in the bizarre position whereby possible suspension is hanging over her for future unspecified behaviour."
The law firm accused Labour of "sloppiness" in its handling of the case and said it could only assume that the rule Dame Margaret is being investigated over is one that relates to actions deemed to be grossly detrimental to the party.
It said it was "perverse" that the same rule used to deal with anti-Semitism in the party is now being invoked against Dame Margaret "for voicing her concern that anti-Semitism has not been properly dealt with".
And it said the result of the disciplinary action against the MP "appears to be pre-determined".