Wigan MP Lisa Nandy has said members cannot allow the Labour Party to be “smashed apart by a polarised, toxic, angry battle” as it faces a leadership crisis.
Ms Nandy, who stepped down from the shadow cabinet this week due to concerns with Jeremy Corbyn, had been tipped to launch a leadership before ruling herself out.
Labour MPs on Tuesday voted for a motion of no confidence in Mr Corbyn who has vowed to re-stand in the event of a leadership election.
Writing in a national newspaper, Ms Nandy said Labour faced a choice of “turn outwards and lead, or inwards to certain destruction.”
She said: “The EU referendum has divided the country, spawning demonstrations, petitions and waves of unease and anger. It has split apart families, friends and neighbours, and it has unleashed dark forces on the far right and hard left of British politics.
“At this critical moment, as Britain renegotiates its relationship with the world, it seems that unease, anxiety and fear have replaced hope, confidence and optimism.
“We cannot allow the party to be smashed apart by a polarised, toxic, angry battle that silences the sensible, committed majority.”
Ms Nandy, along with Makerfield colleague Yvonne Fovargue, was one of more than 40 Labour MPs to resign from the Labour front-bench this week.
She added: “The battle lines in the leadership contest have been drawn, and both sides have signalled they are unwilling to stop. In taking this path we are consigning ourselves to irrelevance at a time when the sensible majority in the country – who want to see a sensible, measured, respectful conversation focused on the things that unite us – desperately need a voice.
“That voice must come from Labour. To make the case for reform to free movement, for economic change that gives us the skills, jobs and industry to survive and to ensure that Britain remains resolutely outward looking as a country both in trade and foreign policy.
“This is the choice before the Labour party: to turn outwards and lead, or inwards to certain destruction. If we choose the latter path we will die, and we will deserve to. It is not too late to change.
“No more threats, anger or despair. Now is the time to reach out, listen and compromise. Decency, respect, solidarity and kindness are our values in this party. And now, more than ever, we must live them.”