In an interview with the 'Dublin People' newspaper, Ms Shortall said there was a very strong desire to see change in the Labour party.
"I am aware of a lot of dissatisfaction from within the party but we haven't got to the point of a heave just yet. I'm not ruling anything out. Anything's possible at this stage," she said.
Ms Shortall directly criticised Mr Gilmore for being part of a government which had "protected the better-off" in the Budget instead of going for alternatives.
"I think there hasn't been a very open leadership and that he hasn't listened to the people," she said.
Ms Shortall has previously blamed Mr Gilmore for refusing to back her in her row with Health Minister James Reilly over the location of two primary care centres in his Dublin North constituency. She quit as junior minister for primary care and also resigned the Labour parliamentary party whip.
But her comments sparked a backlash from Labour TDs, who accused her of "fanciful thinking" and behaving in a "silly way".
They insisted that there was no prospect of a heave against Mr Gilmore and that the party was united behind him.
Dublin South Central TD Eric Byrne said it was an absolute distraction from the work that Labour was doing in Government to get the country back on its feet.
"It's rather immature and certainly not in the tradition of the Labour Party to behave in such a silly way at the beginning of a New Year which is so important for Ireland and Europe," he said.
Mr Byrne went on to say that Labour TDs like Ms Shortall who had lost the party whip clearly liked the "soft life" in opposition after spending more than 15 years there.
And Labour Dublin South- East TD Kevin Humphreys said it was fanciful thinking by Ms Shortall, who had "lost touch" with the parliamentary party.
"I would rule out a heave. There is full confidence in the parliamentary party in Eamon Gilmore," he said.
A spokeswoman for Mr Gilmore declined to comment. Ms Shortall could not be contacted for further comment.