The rising death toll in Gaza's Israel offensive has become "intolerable", the Foreign Secretary has said - while David Cameron has attacked Ed Miliband for "playing politics" over the issue.
Philip Hammond said he had received thousands of emails from the British public expressing horror at the scenes in the Palestinian territory since Israel begun an offensive on July 8.
It comes after a row broke out between Miliband and Downing Street after the Labour leader accused the Prime Minister of getting it "wrong" on Gaza.
Hammond, who was promoted to the Foreign Office three weeks ago, told The Sunday Telegraph: "It's a broad swathe of British public opinion that feels deeply, deeply disturbed by what it is seeing on its television screens, coming out of Gaza.
"The British public has a strong sense that the situation in Gaza is simply intolerable and must be addressed - and we agree with them.
"There must be a humanitarian ceasefire that is without conditions. We have to get the killing to stop."
Earlier, Miliband spoke out against Cameron's handling of the crisis in Gaza, saying the prime minister's failure to oppose Israel's incursion into the Palestinian enclave was "inexplicable".
Miliband condemned Israel's military offensive as "wrong and unjustifiable", and called for the British Government to speak with a united voice to put pressure on both sides to end the violence.
But the Labour leader was accused of "playing politics" and misrepresenting Cameron's position by Downing Street, which insisted the prime minister had always been clear that both sides in the conflict should observe a ceasefire.
A Downing Street spokesman said: "The PM has been clear that both sides in the Gaza conflict need to observe a ceasefire.
"We are shocked that Ed Miliband would seek to misrepresent that position and play politics with such a serious issue."
The 26-day-old offensive, launched in response to rockets fired by Hamas from Gaza into Israel, has now killed more than 1,650 Palestinians - mostly civilians - with more than 8,000 wounded, according to local officials.
Israel has lost 64 soldiers and three civilians, its highest death toll since the 2006 Lebanon war.
Israeli troops were forcing deeper into Gaza after confirming Second Lieutenant Hadar Goldin, who was thought to have been kidnapped by Hamas fighters, had actually been killed in battle.
Hamas denied it was holding Lt Goldin - who is believed to have spent some years living in Cambridge - and suggested he had been killed by an Israeli strike.
In a statement to the House of Commons last month, Cameron voiced "grave concern" about the death toll in Gaza but stressed that Israel had a right to defend itself and accused Hamas of triggering the crisis.
Yesterday, Miliband said the Government must "develop a collective response, not a differentiated one and... speak with one voice".
"We need the clear and unequivocal message that has not so far been provided to be sent from Britain to both sides in this conflict," said Miliband.
"David Cameron and the Cabinet must put Britain in a leading role in pressuring both sides now to end the violence."