David Cameron gave a ringing message of support for Israel this week, telling the community's biggest charity dinner that after more than 100 rockets had been fired into Israel from Gaza in one year, the country had been "within its rights to search vessels bringing cargo into Gaza".

It was a reversal of his remarks in Turkey last July following the seizure of the Mavi Marmara aid ship, when he described Israel's approach to the Gaza flotilla as "completely unacceptable."

But Mr Cameron, who warned that "some people try to judge the Israeli government by a higher code than they would apply to their own government," urged: "Now is not the time to park the Middle East peace process" and asked Israeli leaders and those who supported Israel to "use the developments in the region to seize the opportunity for peace."

He noted that "for decades, autocratic Arab regimes have used the Palestinian cause to smother their own peoples' hopes and aspirations" but believed that young people in the region were waking up to this duplicity.

Mr Cameron's robust remarks to 1100 guests of the Community Security Trust - his second appearance in three years but his first as prime minister - were warm, friendly and bore the hallmarks of someone well aware of the issues most troubling the Jewish community.

Speaking after the Union of Jewish Students chairman, Alex Dwek, had directly asked him to ensure that the Higher Education minister endorsed Manchester University's guidelines for dealing with extremist speakers on campus, Mr Cameron assured his audience that he and his government would do everything possible to confront antisemitism and extremism.

Harking back to his Munich speech last month on the failure of multiculturalism, the prime minister said that: "One of the most immediate threats to the security of the Jewish people comes from the existence of a political ideology which I call Islamist extremism."

He distinguished between Islam and Islamic extremism, saying that young Muslim men had been drawn towards the latter because Britain had not succeeded in integrating them into British society. It had, he said, been a mistake for Britain to "passively tolerate segregated communities."

"The Jewish community is a model of how to integrate," Mr Cameron said. "Proud to be British and proud to be Jewish. If we can get that same sense of national pride and togetherness in all our communities we will all be safer as a result."

On campuses, Mr Cameron drew a distinction between "legitimate debate and illegitimate intimidation."

It was "absolutely right that students and faculty should be able to criticise Israel, in the way that any other country would be criticised. And it is absolutely wrong for students not to be able to express their Jewish identity because of intimidation, and absolutely wrong for university authorities to duck their responsibility in ensuring that there is free speech, and not intimidation."

The prime minister was both scathing and emphatic about his intolerance for extremism. He dismissed attempts to woo young Muslims away from extremism by the use of programmes such as the Prevent strategy. "It would be like talking to the BNP and saying, help us fight Combat 18. We don't do it for fascists and we shouldn't do it for other extremists."

Recalling his own Jewish ancestry - Mr Cameron's great-great-grandfather, Emile Levita, was a German Jewish banker who emigrated to Britain - the prime minister declared: "With me you have a Prime Minister whose belief in Israel is indestructible.

"I will always be a strong defender of the Jewish people, an advocate of the state of Israel, and I will never rest while the Jewish community in Britain is under threat."