Israel has seen its foreign policy allies dropping like flies in 2015, with momentum building behind the boycott, divestment and sanctions (BDS) movement, the Palestinian flag being raised at the United Nations and relations between Israeli Prime Minister Benjamin Netanyahu and US President Barack Obama at historic lows.

Now Jerusalem has lost one of its staunchest allies in Canada's Stephen Harper in the landslide election victory by Justin Trudeau, the 43-year-old son of former prime minister Pierre Trudeau, who won 184 out of 338 seats in parliament in a surprise win for the Canadian Liberal Party.

Harper was known for his refusal to condemn Israeli settlement construction – illegal under international law – and support for Israeli opposition to the P5 + 1 deal between Iran, the US and Europe, which brought to an end Tehran's nuclear weapons programme and raised the prospect of ending decades of isolation for the country.

An editorial in the Times of Israel ahead of the elections claimed Harper was "undoubtedly the world leader most supportive of Israel" and that Israel "was about to lose one of its best friends on the international stage... the Harper administration one Benjamin Netanyahu's dream team".

Canada under Harper has been undeniably pro-Israel, withdrawing financial support for pro-Palestinian NGOs and UNRWA, which operates the bulk of the refugee camps in the West Bank and Gaza. In 2014, he visited Israel with a large entourage of politicians and religious figures and spoke to the Israeli Knesset, when he said: "Through fire and water, Canada will stand with you."

A quintessential neo-con in the model of George W Bush, Harper in a 2003 speech couched foreign policy in firmly moral terms. "The emerging debates on foreign affairs should be fought on moral grounds," he said. "We understand that the great geo-political battles against modern tyrants and threats are battles over values: [...] democracy, free enterprise and individual freedom."

There has been speculation about whether his uncompromising stance has been the influence of radical religious figures on his administration or simply an attempt to attract votes to his Conservative party from Canada's sizeable Jewish community. The Ottawa Citizen reported that on a visit to the Western Wall in Jerusalem in 2014, an aide urged him to pose for a picture, saying: "It's the re-election. This is the million-dollar shot."

Later in that visit, standing next to Netanyahu, Harper said: "I'm not here to single out Israel for criticism."

The loss of such a committed ally comes as Netanyahu looks increasingly isolated on the world stage. The nuclear deal with Iran was widely praised internationally, with Israel and the states of the Gulf alone forced into a bizarre coalition against what is undoubtedly Obama's legacy project. It came after a year of increasingly fraught relations between the US and Tel Aviv, culminating in Netanyahu's controversial address to US Congress.

Meanwhile, the recognition of Palestine by France and Sweden and the raising of the Palestinian flag at the UN in September have come as momentum builds behind the BDS movement. The EU banned dairy products made on Israel settlements in January and is believed to be close to enacting a long-delayed plan to label products made on occupied Palestinian land.

But the question is whether Trudeau will necessarily reverse the policies of the Harper government with regard to Israel. During debates in the run up to the election, he argued there was little difference between Conservative and Liberal support for Israel.

Like most leaders, the new prime minister has expressed his support for a two-state solution to the Israel-Palestine conflict in typically vague terms, calling for negotiations that any serious analysis suggests are unlikely. Equally vague is Trudeau's comment to a Canadian Jewish newspaper that "unilateral actions by either side" had hindered efforts to secure peace in the region.

But he has been more outspoken about the BDS movement, which he has not only opposed but branded as "an example of the new anti-Semitism in the world". In this, he echoes the exact words of Harper, who described the BDS movement in exactly the same terms in May.

He told Canadian Jewish News: "I'm all for freedom of speech and expression in Canada, and we need to be sure we're defending that. But when Canadian university students are feeling unsafe on their way to classes because of BDS or Israel Apartheid Week, that just goes against Canadian values."