The raid on the Gaza aid flotilla was "completely unacceptable" David Cameron said today.
In his first question time as Prime Minister, Mr Cameron said he deplored the loss of life.
"We should do everything we can to make sure this doesn't happen again," he told a crowded Commons, moments before Foreign Secretary William Hague was due to make a statement on the killing of several civilians in the Israeli-led raid.
"Friends of Israel - and I count myself a friend of Israel - should be saying to the Israelis that the blockade actually strengthens Hamas's grip on the economy and on Gaza, and it's in their own interests to lift it and allow these vital supplies to get through."
More than 40 Britons detained during the raid on the aid flotilla were being released and deported today.
In total, 679 people were taken prisoner during the Israeli military-led action which saw nine civilians killed.
Acting Labour leader Harriet Harman said: "This is a tragic loss of life which has angered the Palestinians and dismayed friends of Israel too.
"What's the current position of the British nationals detained by the Israelis?
"Will you tell us how the Government can contribute to international efforts to make the Israelis recognise that the blockade of Gaza is prolonging the suffering of the Palestinians and making peace in the middle east even harder to achieve.
"This blockade must end."
Mr Cameron told her: "What has happened is completely unacceptable. We should be clear about that and we should also deplore the loss of life - and I've spoken to the Prime Minister of Turkey to extend our condolences for the Turkish citizens who have been lost.
"We should do everything we can to make sure this doesn't happen again - and I stressed this point in a conversation with President Netanyahu of Israel."
Mr Cameron said 42 British nationals were "caught up" in the raid.
"I believe that around 37 of them have had consular access and all of them will be coming home, and we need to make sure they are reunited with their families as fast as possible."
He added: "We should do everything we can through the UN, where resolution 1860 is absolutely clear about the need to end the blockade and to open up Gaza."Reuse content