The Labour MP for Leeds North East, Fabian Hamilton, says it is becoming more and more difficult to defend Israel in the House of Commons.
The long-serving Jewish MP represents Alwoodley, Moortown and Roundhay, home to the majority of Leeds' 8,000 Jews.
He said: "Labour Friends of Israel is still quite strong, as are the Conservatives. But there is a stronger pro-Palestinian lobby too. Some of Israel's mistakes have really strengthened them.
"If you're a neutral MP, you'd think the flotilla was appalling - it's bound to pull you in a certain direction. They [Israel] might have had a damn good reason to do what they did to the Gaza flotilla but, my God, it was bad PR and the Palestinian lobby is unfortunately capitalising on that."
Mr Hamilton said he loved the country but was not a "slavish" supporter of Israel. "I want Israel to be admired, not just by Jews, but by Muslims and everyone.
"That's not happening right now, and the Israelis don't give a damn.
"They have to pay heed to this. It's awful to hear what some people think of Israel, when you think how much Israel has achieved. I love Israel, and we are losing the front.
Before the election, when he was a member of the Foreign Affairs Committee, Mr Hamilton lobbied for changes to universal jurisdiction. He said: "The whole committee pressed Jack Straw and David Miliband. We were very, very angry it did not happen.
"I met Tzipi Livni in February and she has been treated appallingly. It's a total abuse of a law set up to deal with Yugoslavian and Sudanese war criminals - people who committed genocide.
"The idea that Livni has anything in common with them is just outrageous. It's almost antisemitic, frankly."
Now after 13 years as a backbencher, and nine on the Foreign Affairs committee, Mr Hamilton is looking for new challenges. He said: "I'm supporting David Miliband for Labour leader because he's the best candidate by far. I have worked hard to help him."
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