Boris Johnson has been accused of descending to “crude insults” in the general election battle after using a lewd biblical term in an attack on Jeremy Corbyn.

In his first keynote speech of the election campaign on Wednesday, the prime minister will accuse the Labour leader of political “onanism” – an arcane word meaning masturbation.

Extracts released by Conservatives ahead of the speech showed that the PM will also complain that the Brexit debate has become mired in “groundhoggery”.

But he will follow up on his reference to the movie Groundhog Day – in which the same day is repeated on an endless loop – by recycling well-worn slogans about “getting Brexit done” and avoiding a “horror show” coalition between Mr Corbyn and Scottish National Party leader Nicola Sturgeon.

He will repeat his claim that defeat for the Conservatives in the 12 December poll would mean referendums on both EU membership and Scottish independence in 2020.

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And he will say: “We can honour the wishes of the people, or else we can waste more time, at the cost of a billion pounds per month, and have two more referendums, one on Scotland and one on the EU – an expense of spirit and a waste of shame, more political self-obsession and onanism.”

Responding to the prime minister’s comment, a Labour source said: “We’re not bothered by Johnson’s obscure, crude insults because we’ve got our eyes on the prize – real change for the many not the few.”

Speaking at an electric vehicle manufacturer in the West Midlands, Mr Johnson will admit that countries around the world are “baffled” that the UK has squandered three years of time and energy on the Brexit debate.

He will claim that a Conservative majority government would get the UK “out of the rut” and “end the groundhoggery of Brexit”.

And he will promise to drive a clean energy revolution to tackle climate change, spur economic growth and create high-skilled jobs.