Physical assaults against Jewish people have doubled and harassment reached an all-time high, according an audit of antisemitic incidents recorded in the United States in 2018.

The Anti-Defamation League recorded 1,879 antisemitic incidents across the United States, with the highest number of cases in more than a decade connected to extremist individuals or groups.

Figures published on Tuesday revealed the most incidents were recorded in California (341) and New York (340). Together with New Jersey and Massachusetts, the four states accounted for more than half of all incidents in the country.

The audit covers incidents in 2018, including the white supremacist shooting spree at a Pittsburgh synagogue which killed 11 people, but not last weekend's shooting in San Diego.

The previous ADL audit had recorded the largest year-on-year rise in antisemitism since 1979, when the organisation first began tracking cases of harassment of Jewish people, vandalism of Jewish property and physical assaults.

ADL chief executive Jonathan Greenblatt said his organisation has grown concerned by “a disturbing uptick in incidents over the past three years.”

The rise corresponds with the period after Donald Trump was elected President of the United States, a development that critics have said emboldened far-right activists.

Former Vice President Joe Biden, who is seeking the Democratic nomination to challenge Mr Trump in the 2020 election, said last year that Mr Trump’s leadership was “giving licence to this prejudice.”

The ADL audit recorded 1,066 cases of antisemitic harassment, far above the 721 incidents recorded just two years previously, and a 105 per cent increase in assaults.

“While many of the incidents we track might seem relatively minor — a swastika drawn on a student’s notebook or a stereotype aimed at a pro-Israel college student — we refuse to ignore these ‘small’ incidents,” Mr Greenblatt said.

“We will not do so because dismissing such acts only serves to normalise antisemitism. If we don’t stop the smaller incidents in their tracks, we may end up with major acts of violence.”

This year’s study recorded a slightly lower number of overall incidents compared to the previous 12 months, in part because the number of antisemitic vandalism cases fell from 2017.