As he stood on two Iron-Bru crates campaigning for a "No" vote in last year's Scottish referendum, Jim Murphy's support for Israel was frequently hurled at him as a term of abuse by pro-independence hecklers.

Four months after Labour Party members selected him to halt the Scottish National Party's surge in the polls - which threatens to wipe out Labour north of the border and with it Ed Miliband's chances of making it to Downing Street - Mr Murphy remains unintimidated.

"I was a friend of Israel before I became a member of Parliament and I will be afterwards. It's a life-long commitment to the idea and to the democracy of Israel," he said.

Mr Murphy was quick to denounce the rise in antisemitism which accompanied last summer's war between Israel and Hamas. It should "never be left to the Jews to stand against antisemitism. That has to be an unconditional", he argued.

"The Jewish community should never look to the left, to the right or over their shoulder and not find friends. They should never be alone. That's non-negotiable. That's no matter who you upset. No matter who you annoy."

Why then the slow and muted response from his party's leadership? "The Labour party has never and will never tolerate orchestrated or spontaneous acts of antisemitism," Mr Murphy said.

"A Britain with Ed as Prime Minister will continue to be clear that antisemitism is a poison that, left unchallenged, would spread."

Mr Murphy, whose East Renfrewshire constituency is home to a large proportion of Scotland's small Jewish community, is keen to dismiss the notion that a Miliband government would not be a reliable friend of Israel.

"I've spoken to Ed about this and I don't have any doubts about his sincerity. Nor do I have doubts about his determination to set aside time to make sure there's a genuine effort for a two-state solution, which respects Israel's security needs and honours the Palestinians' entirely legitimate and overdue right to a state."

The doubts about Mr Miliband in some parts of the Jewish community - fuelled by his stance over Operation Protective Edge and the vote on Palestinian statehood last autumn - are exacerbated by a fear that, short of a majority, Labour may be forced to rely on support from the SNP with its anti-interventionist foreign policy and pronounced hostility to Israel.

Mr Murphy, a former chair of Labour Friends of Israel, said his party was "not going to ask the SNP's permission before we put our policies to the House of Commons".

Given the SNP's pledge not to support a Tory government under any circumstances, Mr Murphy suggested "the only other place for them to go is to support a Labour government, so they have no power over us".

The Scottish Labour leader is, however, determined to avoid placing Mr Miliband at the mercy of the nationalists.

He acknowledges that current polls in Scotland are bad for Labour, but believes the gap will close.

"I think it will change big and it will change late," he said, as voters focus on the fact that May's vote is "not referendum round two, but whether David Cameron should get a second term in Downing Street".