Campaigning ahead of the general election on Thursday has resumed following the terror attack in London over the weekend.
The leaders had suspended the campaign after the car and knife attack on London Bridge and Borough Market on Saturday night which killed seven people.
The parties are to due to set out their security credentials, while Prime Minister Theresa May has been chairing a meeting of senior ministers and security chiefs at the government's emergency Cobra committee this morning.
May has returned to her theme of strong and stable leadership, while Labour leader Jeremy Corbyn and the Lib Dems have been criticising her cuts to the police force.
Downing Street sources said the prime minister will be delivering a speech pledging leadership to keep the country safe from terrorism, making a Brexit deal, and managing the economy.
Following the London Bridge attack, May said the internet must be regulated in a bid to 'deprive the extremists of their safe spaces online'.
'We cannot allow this ideology the safe space it needs to breed - yet that is precisely what the internet, and the big companies that provide internet-based services provide,' the PM said outside Downing Street yesterday.
'We need to work with allied democratic governments to reach international agreements to regulate cyberspace to prevent the spread of extremist and terrorism planning.'
The Tory party manifesto pledges the regulation of the internet, but many have taken to Twitter to condemn May's language:
May's comments come after the third terror attack in the UK in three months. In March in Westminster, a car and knife attack killed five people. A suicide bombing in Manchester Arena on May 22 killed 22, and injured 59.
The general election will go ahead as planned on June 8.