An open letter has been signed by 44 Anglican leaders, pleading with the UK government to help the drought-ravaged Horn of Africa.
Bishops from east Africa are appealing in a bid to urgently get more funding to those in need.
They warn Britain's rapid response to the Ukraine crisis must not come at the expense of lives elsewhere.
Faith leaders wrote in the letter - seen by the Guardian: "This must change. "Every day, more lives are lost, and more are at risk."
The bishops wrote: "We call on the UK government to urgently get more funding to the frontline of the hunger crisis in east Africa, and to mobilise the international community to collectively step up.
"Early warnings were not heeded. Existing commitments to strengthen resilience have not been backed up by funding that is so desperately needed."
Most Rev Justin Badi Arama, Archbishop of South Sudan, is included in the group and said while "another famine is on the horizon", it is not inevitable.
The letter has also been backed by Most Rev Justin Welby, Archbishop of Canterbury, who said: "The crisis in east Africa has been building for at least two years and is now devastating the people of
the area and threatening worse.
"I appeal to our government and to the people of this country: please step forward to enable food to be purchased."
Somalia, Ethiopia and Kenya are experiencing the worst drought in four decades, with millions facing acute hunger.
The UK government gave £220 million in humanitarian assistance to Ukraine.
The bishops, from Kenya and South Sudan, commend that "generous" effort, but warn: "This should not be a reason to divert humanitarian resources away from regions also in dire need, such as ours.
"Saint Paul wrote that we are all part of one body, we are interdependent. For the sake of the whole body, sisters and brothers, we need your help."
The message came as a ship carrying wheat from Ukraine to the Horn of Africa docked in Djibouti, the first to make the journey since the war began in February 2022.
The World Food Programme spokesperson said 23,000 tonnes of grain are destined for Ethiopia and will cover 1.5 million people's needs for a month,
He cautioned, however, that the delivery was a start that must be followed up by more shipments.