WIRRAL West's Margaret Greenwood was one of 56 Labour MPs who voted to support an SNP amendment to the King’s Speech backing a ceasefire in Gaza.
Labour leader Sir Keir Starmer lost eight frontbenchers after he suffered a major rebellion in the Commons vote last night.
Four shadow ministers, including Jess Phillips, Yasmin Qureshi, Afzal Khan and Paula Barker, quit on Wednesday evening.
Four other frontbenchers: Rachel Hopkins, Sarah Owen, Naz Shah and Andy Slaughter; have also left the front bench after breaking the party whip to back the amendment.
Parliamentary private secretaries Dan Carden and Mary Foy have also left their positions.
MPs voted 293 to 125, majority 168, to reject the SNP’s King’s Speech amendment calling for “all parties to agree to an immediate ceasefire” in Gaza.
But 56 Labour MPs backed the position, rejecting their party leader’s stance.
Labour MPs had been ordered to abstain on the SNP move and were told instead to back Sir Keir’s position calling for longer “humanitarian pauses” rather than a ceasefire.
The party has been riven with internal divisions over Israel’s response to the deadly incursion by Hamas that sparked the conflict.
The leadership has backed the UK Government’s position of pushing for humanitarian pauses in the fighting to allow aid to reach Palestinians trapped in the bombarded territory but has stopped short of calling for a total cessation of hostilities.
Birkenhead MP Mick Whitley said that as a result of a family emergency he had been unable to be in Parliament to vote but confirmed in a statement that he would have joined the rebels in voting for a ceasefire.
Mr Whitley said: "I want all of my constituents to know that, if I was (able to vote), I would be voting for a ceasefire this evening even if that meant defying my party's whip.
"Throughout this conflict, I have been consistent in my calls for an urgent ceasefire and the immediate and unconditional release of hostages. A comprehensive ceasefire, is in my view, the only way of securing the unimpeded entry into Gaza of the humanitarian aid that the civilian population so desperately needs. It is also an essential precondition for the beginning of a new political process aimed at securing a lasting and equitable peace for Palestinians and Israelis alike.
"To this end, I have joined colleagues from across the House of Commons in supporting early day motions and amendments to the King's Speech calling for an immediate ceasefire.
"I am concerned that by failing to follow the lead of the more than 120 countries who recently voted in favour of a ceasefire at the United Nation's General Assembly, the British Government is failing to demonstrate the moral leadership that the public rightly expects.
"I also regret that the position of my own party's front bench fails to support the comprehensive ceasefire that is needed to address the scale of the humanitarian crisis that is unfolding in Gaza."
Wallasey MP Angela Eagle, Ellesmere Port and Neston MP Justin Madders and Wirral South MP Alison McGovern all abstained in the vote.