Jeremy Corbyn is to draw a direct link between British foreign policy and terror attacks such as the Manchester suicide bombing.
The Labour leader will resume his election campaign with a speech in central London on Friday morning, when he will say his government would tackle “the causes of terrorism” as well as reverse police cuts.
Britain “must be brave enough to admit the war on terror is not working” and find “a smarter way” to tackle the threat, he will say.
But the pre-briefed extracts of his speech were swiftly criticised by the Liberal Democrats, who said that it was too soon after the devastating Manchester attack to “seek political advantage”.
In his first intervention since the suicide bomb attack which left 22 dead at the Ariana Grande concert, Corbyn will talk about security, British values and call for a change in foreign policy.
“Many experts, including professionals in our intelligence and security services, have pointed to the connections between wars our government has supported or fought in other countries and terrorism here at home,” he will say.
“That assessment in no way reduces the guilt of those who attack our children. Those terrorists will forever be reviled and held to account for their actions.
“But an informed understanding of the causes of terrorism is an essential part of an effective response that will protect the security of our people that fights rather than fuels terrorism.
“We need a smarter way to reduce the threat from countries that nurture terrorists and generate terrorism.”
Corbyn has been criticised in the past for his reluctance to back a shoot-to-kill policy in the event of a terrorist incident.
Earlier in the election campaign, which was suspended for three days after the horror unfolded at Manchester Arena on Monday, the Labour leader said he was ‘not a pacifist’.
In Friday’s speech he will say no government can prevent every terrorist attack.
“If an individual is determined enough and callous enough sometimes they will get through,” he will say.
“But the responsibility of government is to minimise that chance - to ensure the police have the resources they need, that our foreign policy reduces rather than increases the threat to this country and that at home we never surrender the freedoms we have won and that terrorists are so determined to take away.”
He will also point to Labour manifesto commitments to reverse cuts to emergency services and put 10,000 more police on the streets.
“I want the solidarity, humanity and compassion that we have seen on the streets of Manchester this week to be the values that guide our government. There can be no love of country if there is neglect or disregard for its people,” Corbyn will say.
Former Leader of the Liberal Democrats Paddy Ashdown said: “Some political leaders have sought to politicise the events of the week, but now is not the time, and this is not the event, to seek political advantage.
“The families of victims in Manchester have a right to expect political parties to respond with restraint and sensitivity to these unpardonable crimes.”
The Conservatives and Lib Dems will also resume national election campaigning on Friday.