Theresa May has attacked Jeremy Corbyn for abandoning "patriotic working class people" while the Labour leader has hit back with an accusation that she is "pandering" to Donald Trump.
In what looks set to be the most bitterly personal exchanges of the General Election to date, the two leaders will trade blows in rival speeches as the campaign turns nasty.
The Prime Minister will seek to capitalise on the chaos in Labour after the leak of its draft election manifesto with an ambitious foray into the party's North East heartlands where she will make a direct appeal to voters to put their trust in her.
Mr Corbyn will use his speech to a leading international affairs think tank to try to cast off his image as a pacifist unwilling to take military action while denouncing Mrs May's closeness to the Trump administration in Washington.
With some moderate Labour MPs reported to be in revolt over Mr Corbyn's radical programme of renationalisation and expanding public services, Mrs May will accuse him of a return to the "disastrous socialist policies of the 1970s".
In a speech marking the mid-point of the campaign, she will reach out to disaffected Labour voters, saying many were "appalled" at the direction he was taking the party, while promising to "earn the trust of all our people" if she is returned to Downing Street on June 8.
"So far during this campaign we have learned one thing about Jeremy Corbyn: proud and patriotic working class people in towns and cities across Britain have not deserted the Labour Party - Jeremy Corbyn has deserted them," she is expected to say.
"Millions of people here in the North East of England, and across our country, have loyally given the Labour Party their allegiance for generations. I respect that.
"We respect that parents and grandparents taught their children and grandchildren that Labour was a party that shared their values and stood up for their community.
"But across the country today, traditional Labour supporters are increasingly looking at what Jeremy Corbyn believes in and are appalled."
In his speech to the Chatham House think tank in London, Mr Corbyn will insist he is not a pacifist, and will do "everything necessary" to protect the country if he is elected.
At the same time, he will condemn the "bomb first, talk later" policies of recent British and US governments and will promise to pursue an independent foreign policy "made in London", which protects UK interests by seeking peaceful solutions to conflicts around the world.
"Waiting to see which way the wind blows in Washington isn't strong leadership. And pandering to an erratic Trump administration will not deliver stability," he will say.
"Britain deserves better than simply outsourcing our country's security and prosperity to the whims of the Trump White House.
"So no more hand-holding with Donald Trump - a Labour government will conduct a robust and independent foreign policy made in London."
Mr Corbyn, a long-standing critic of interventions in Iraq, Syria and Afghanistan, will say that the US-led "war on terror" which followed the 9/11 attacks of 2001 had failed to deliver security and that a new approach was needed.
"I am not a pacifist. I accept that military action, under international law and as a genuine last resort, is in some circumstances necessary," he will say.
"But that is very far from the kind of unilateral wars and interventions that have almost become routine in recent times."
Shadow foreign secretary Emily Thornberry warned that a Tory victory would lead to the UK becoming embroiled in the Syrian civil war in a sign of Mrs May's "devotion" to Mr Trump.
"A disregard for human rights leads to disdain for the human consequences of war," she wrote in The Guardian.
"If she wins on June 8, as a fresh act of devotion to Trump, she will call an immediate vote on military action against the Syrian government. Not only would that escalate and prolong the war in Syria, it would risk bringing us into conflict with Russia and Iran - and all without any UN agreement or authorisation."
Under Mr Corbyn, Labour will return to the "ethical" foreign policy championed by Robin Cook.
Labour will "strive to reduce not increase global tensions, and give new momentum to talks on non-proliferation and disarmament", Ms Thornberry said.
The party would put human rights "back at the heart of foreign policy" and "stand up" to the Trump administration, she added.