Ian Murray has said he could run as an independent candidate if he is deselected by Labour.
The Edinburgh South MP spoke out after reports the Unite union is to attempt to trigger a deselection process against him.
Under Labour Party rules, a contest to replace a sitting MP is triggered if a third of local members or affiliated unions back it.
Mr Murray – who has been a vocal critic of Jeremy Corbyn’s stance on Brexit – said installing a “hard left Marxist candidate” in his place would see Labour lose the seat.
Mr Murray won the Edinburgh South seat for Labour in 2010 and became the party’s only Scottish MP five years later when a wipeout north of the border saw them lose 40 out of the 41 seats.
He insisted an attempt by the Unite union to deselect him would be unsuccessful – but added that if it did happen he would have a “decision to make” on whether to stand as an independent candidate.
Mr Murray told BBC Radio Scotland’s Good Morning Scotland programme: “If Unite want to try to deselect me on Thursday I am sure the membership of South Edinburgh – that I get on very well with and have their full, wholehearted support – will take a very dim view of and will vote accordingly.”
Pressed on what could happen if he was ousted from the candidacy, he added: “I would have a decision to make about whether I would stand.
“I think constituents deserve to have a choice of candidates in front of them, I would obviously discuss that with friends, family and colleagues to decide whether or not I would stand if I was deselected.
“But certainly I can guarantee that if the Labour Party … put in some hard left Marxist candidate they won’t win the seat of Edinburgh South.
“That would be damaging to the Labour Party and damaging to the country.”
Mr Murray said he had not spoken to the Labour Party leadership about the move to deselect him.
However, he said he would “expect” their support, adding: “If Jeremy Corbyn wants to be prime minister then south Edinburgh has to be a seat we continue to hold for the Labour Party.”
Former Labour deputy leader Harriet Harman branded reports Mr Murray could be ousted from his constituency as “total madness”.