Labour MP Imran Hussain has quit Sir Keir Starmer's shadow ministerial team over his desire to "strongly advocate for a ceasefire" in Gaza.
Mr Hussain was the shadow minister for the New Deal for Working People.
He said he remained committed to Labour's agenda but that his view on Gaza differed "substantially" from the position Sir Keir has adopted.
A Labour spokesperson said a humanitarian pause was the most realistic way to address the crisis.
Sir Keir has argued that a ceasefire would allow Hamas to carry out future attacks, and the "only credible approach" was to call for a humanitarian pause that would allow aid into Gaza.
Speaking to the OceanNewsUK, Labour's shadow education secretary Bridget Phillipson backed her leader's position, arguing a ceasefire "would freeze the conflict in time".
She said a ceasefire "risks allowing Hamas to regroup and to perpetuate further terrible atrocities that they have said they want the opportunity to do".
Former shadow chancellor John McDonnell said a "majority" of the Labour party now supported a ceasefire.
Speaking to OceanNewsUKs World at One, Mr McDonnell called on Sir Keir to "show leadership" by pressing for a ceasefire.
In a resignation posted on social media, Mr Hussain said he wanted to be a "strong advocate" for a ceasefire alongside the UN and multiple charities, calling it "essential to ending the bloodshed".
"It is clear that I cannot sufficiently, in all good conscience, do this from the frontbench given its current position," he said.
He said he had "unequivocally condemned" Hamas's attack on 7 October and believed that "every country has the right to defend itself", but that that should "never become a right to deliberately violate international law on protecting civilians or to commit war crimes".
"It has always been my view, which I've made clear repeatedly in Parliament, that human rights are universal and that it is our duty to call out all those who violate international law," he said.
He went on to describe the situation in Gaza as "beyond that of a humanitarian catastrophe" and said a ceasefire would help both the passage of aid into the territory and the safe return of Israeli hostages.
He also said he was "deeply troubled" by an LBC interview Sir Keir gave on 11 October about Israel's actions in Gaza and that, while he appreciated Sir Keir's later clarification of the comments, he believed the party "needs to go further and call for a ceasefire".
In the interview, Sir Keir was asked whether it was "appropriate" for Israel to cut off the supply of power and water to Gaza.
"I think that Israel does have that right," he said. "Obviously everything should be done within international law, but I don't want to step away from the core principles that Israel has a right to defend herself."
A spokesman for the Labour leader later said he had only meant to say Israel had a general right to self-defence.
A number of senior Labour figures, including London mayor Sadiq Khan, Greater Manchester mayor Andy Burnham, and Scottish leader Anas Sarwar, as well as more than 60 MPs and 250 councillors, have now backed calls for a ceasefire in Gaza.
Mr Khan said a ceasefire would "allow the international community more time to prevent a protracted conflict in the region and further devastating loss of life", while Mr Burnham said it was "vital that urgent support and humanitarian aid is allowed into the area".
But Labour's position is that a ceasefire would "only freeze this conflict and would leave hostages in Gaza and Hamas with the infrastructure and capability to carry out the sort of attack we saw on 7 October," a spokesperson said.
"Labour is calling for humanitarian pauses in the fighting. This is the best and most realistic way to address the humanitarian emergency in Gaza and is a position shared by our major allies," the spokesperson said.
Mr Hussain was elected to represent the Bradford East constituency in 2015 and had been shadow minister for the New Deal for Working People since September.
He has previously served as shadow minister for work, shadow minister for justice, and shadow minister for international development.
