Anyone who endorses settlement building should be treated as an "extremist" who is unfit to be an MP, a former minister said in an outspoken attack on the Israeli government and its supporters.

Alan Duncan criticised the international community for failing to condemn Israel over the policy - which he compared with South Africa's apartheid system - revealing that he raised his concerns with David Cameron last year while he was international development minister.

He was one of 274 MPs who last night overwhelmingly approved a Commons motion urging the Government to recognise Palestine as a separate state.

Ministers, who are not bound by the result of the highly-symbolic vote, insisted the time was not right for the change of stance.

Mr Duncan used a speech to the Royal United Services Institute (Rusi) to demand a rethink of Middle East peace policy, including an end to the world's unwillingness to "rock the boat" by criticising Israel.

"It is a poor reflection on the international community, and on the United States in particular, that Israel persists with the building of settlements largely because it believes that it can get away with doing so," he said.

"Whatever their other arguments, whatever their deliberate attempts to divert attention from the issue, the continuing gradual annexation by Israel of their neighbour's land is an ever-deepening stain on the face of the globe.

"No end of diversion, deceit or delay should be allowed to detract from this undeniable principle. Israeli settlements are illegal, and until Israel admits as much, and behaves accordingly, Israel forfeits its moral standing.

"Whatever Israel's approach may be, the rest of the world can and should make its own stand. If it fails to do so, then there is little morality left in international politics."

Israel had showed it had "little or no intention of ending that occupation or of permitting a viable Palestinian state to come into existence", he said.

"Occupation, annexation, illegality, negligence, complicity: this is a wicked cocktail which brings shame to the government of Israel. It would appear that on the West Bank of the Jordan the rule of international law has been shelved.

He added: "One should not use the word 'apartheid' lightly, but as a description of Hebron it is both accurate and undeniable."

No-one had the right to question Israel's existence, he stressed, but he hit out at some Jewish organisations for painting critics of the Israeli government as anti-Semitic.

Most Israelis and Jewish people in the UK were "unhappy" about settlements, he argued.

And arguing in favour of the building programme should be placed "on a par with racism, sexism, homophobia and anti-Semitism".

"Just as we quite rightly judge someone unfit for public office if they refuse to recognise Israel, so we should shun anyone who refuses to recognise that settlements are illegal," he argued.

"No settlement endorser should be considered fit to stand for election, remain a member of a mainstream political party, or sit in a Parliament. How can we accept lawmakers in our country, or any country, when they support lawbreakers in another? They are extremists, and they should be treated as such."

Mr Duncan said the most recent settlement plan, involving the Givat Hamatos neighborhood in southern Jerusalem, was a "calculated insult to President Obama" and made it "impossible to overstate the criminal intent and strategic importance of Israel's settlement plan".

"For far too long, those who have made a moral stand against Israeli misconduct and in favour of justice for Palestinians have been trashed, traduced and bullied. This, and the character assassination of critics, cannot be allowed to continue," he concluded.

"The time has come for us to make an international stand on the principle of illegal Israeli settlements.

"All who converse, all who interview, and all who debate are entitled to ask their interlocutor for a simple answer to a simple question. 'Do you agree that Israeli settlements outside the 1967 borders are illegal - yes or no?'

"If they give no answer at all, or equivocate, or actually say 'no', then we are entitled to brand such a person morally complicit in illegality, and therefore an extremist.

"They are not fit to stand for election or sit in a democratic parliament, and they should be condemned outright by the international community and treated accordingly."

Tory MP Mike Freer quit as a ministerial aide to Skills Minister Nick Boles so he could vote against the recognition of Palestine as a state.

Mr Freer, whose Finchley and Golders Green seat covers the heart of north London's Jewish community, said he felt obliged to represent his constituents but was not supposed, as a parliamentary private secretary (PPS), to take part in the vote.

Mr Duncan published a letter he sent last year to then-foreign secretary William Hague - and copied to the Prime Minister - urging them to harden the UK's stance on settlement building.

Despite publicly disputing the policy, "our words are not followed by any action or even indignation whenever further settlements are constructed", he complained.

There would be widespread support at home and around the world if Britain was to "make the moral stand from which we have always resiled and move from regret to outright condemnation".

Israel's defence that the work was needed to protect its security was "no more than an excuse", he said.

Israel's ambassador to the UK, Daniel Taub, denied that the Commons vote was a sign of his country "haemorrhaging support" in Britain.

Mr Taub told BBC Radio 4's World at One: "I don't think we are haemorrhaging support. I think there's a lot of frustration that there hasn't been more progress in the peace process with the Palestinians, and we - the Israelis - are party to that.

"The problem in reaching a peace agreement has never been the Israeli settlements. The fact that we have something less than 2% of West Bank land, which would all have been included in areas which would be land-swapped, has never been the reason."

He added: "When we think about the problems that are actually frustrating an agreement, the primary one is the fact that the Palestinian leadership is still not capable of recognising the idea of a Jewish state. For close to two decades, we haven't had a single Israeli prime minister who has not recognised the need to establish a Palestinian state."