Tony Blair was under growing pressure to stand up to George Bush last night after 37 children were killed in an Israeli bombing raid on Lebanon.
One of his staunchest allies, Birmingham MP Khalid Mah-mood, described Britain's stance as "outrageous" and called for the Government to urge the US to take action to stop the bloodshed.
"It is outrageous that we are standing by and watching this go on," he said. "Enough is enough and we need to be far more vocal in calling for Israel to stop."
Mr Mahmood (Lab Perry Barr), one of the few Muslim MPs in the Commons, has generally supported the British Government's foreign policy, including the close alliance with the United States.
His comments followed reports that the Cabinet is split over the Middle East crisis, with Jack Straw, the Leader of the Commons and former Foreign Secretary, attacking Israel's "disproportionate" offensive.
Mr Blair's spokesman denied the Cabinet was divided yesterday. He said the Prime Minister did not endorse or criticise Mr Straw's remarks.
But Mr Blair and President George Bush have refused to call for an immediate ceasefire, arguing that Hezbollah's rocket attacks on Israel must end for any peace agreement to be sustainable.
At least 60 civilians, 37 of them children, died in an Israeli air-strike on the town of Qana in southern Lebanon.
Last night Mr Blair described the destruction of Qana as "an absolutely tragic situation" and called for an immediate United Nations resolution to halt the Middle East bloodshed.
Mr Mahmood said: "We cannot continue saying we are working towards peace in the Middle East and allow things like this to go on.
"I think Jack Straw has hit the nail on the head. We need more people to raise the issue, and the Prime Minister to take the lead.
"I think it is deliberate targeting of women and children. We have to condemn it and put a stop to it.
"It is true that only the United States really has the power to make it stop, but if Britain spoke out I think the US would listen.
"I wholly condemn the attacks by Hezbollah on innocent people in Israel, but equally we must condemn attacks by Israel on innocent people in Lebanon."
Meanwhile Selly Oak MP Dr Lynne Jones was one of nine Birmingham women deported from Israel yesterday on a mission to build peaceful links between Britain's second city and that of Ramallah.
She described their treatment as "quite appalling" and claimed the refusal was a clumsy bid by the Israelis to screen from public view what was happening in Palestine.
The women were taking books and money raised by Birmingham's Ramallah Twinning Committee to create a library at a refugee camp. The MP had joined the group after a similar peace visit by the group, which included Yvonne Washbrook, president of Birmingham Trades Council, and Salma Iqbal, a Respect Coalition candidate in the last Birmingham City Council elections, was turned away last year.
The Israeli embassy was informed of their detailed itinerary, flights and passport numbers beforehand to facilitate access into the country. But on arrival at Tel Aviv airport at 3.45am yesterday the group, after interrogation, were sent to a detention centre then put on a flight home.
Dr Jones said: "I find it horrendous that the Israeli authorities can deny entry to what should be an independent Palestinian state, so we can't get there to see what they are doing.
"First they said they did not know anything about our trip, and when challenged they changed their tune. We were in constant contact with the British Embassy and the Israeli Foreign Affairs Ministry and the Ministry of the Interior, and it was clear they had all the details about our trip.
She said they were kept for 11 hours with only water to drink, and the interrogation had reduced one of their group to tears.
"I will come again on parliamentary business if I can and I will look for the opportunity to confront the people behind this outrageous decision," she said.