Theresa May declared “enough is enough” as she announced plans to introduce new anti-terror laws in the wake of the London Bridge attack.
Speaking outside 10 Downing Street, the prime minister warned there had been “far too much tolerance of extremism” in the UK, as she promised a review of counter-terrorism strategy and said new international agreements must be introduced to regulate the internet.
But critics accused her of politicising the atrocity in breach of an agreement to halt the general election campaign.
The Labour leader, Jeremy Corbyn, accused the prime minister on Sunday night of trying to “protect the public on the cheap” by implementing 20,000 police cuts.
The attack in the centre of the capital in which seven people were killed came just days before Thursday’s general election with the polls in flux. Six separate polls over the weekend showed a Tory lead over Labour of between one and 12 percentage points.
In her address, following a Cobra emergency meeting, May said that internet companies must not allow extremism a place to exist.
“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,” she said.
“We need to work with allied democratic governments to reach international agreements to regulate cyberspace to prevent the spread of extremism and terrorism planning,” she said.
Her comments followed the decision by the Conservatives, Labour, the SNP and Liberal Democrats to suspend election campaigning until Sunday night.
The prime minister suggested there could be increased prison terms for terrorism offences, even relatively minor ones.
Islamist militancy was the thread that linked the otherwise unconnected recent attacks in London Bridge, Westminster and Manchester, she said.
“It is an ideology that is a perversion of Islam and a perversion of the truth,” she said. “Defeating this ideology is one of the great challenges of our time. But it cannot be defeated through military intervention alone.”
May said the recent spate of attacks showed the UK was “experiencing a new trend in the threat we face”.
Action was needed in the UK as well as overseas, she added. “While we have made significant progress in recent years, there is – to be frank – far too much tolerance of extremism in our country.”
She said that campaigning would resume and the election would still take place on 8 June.
The foreign secretary, Boris Johnson, formerly London’s mayor, echoed May’s words. He said: “The wells of tolerance are running empty.”
It is the second terrorism-related suspension of the campaign. It stopped for three days after the suicide bomb attack in Manchester, on 22 May, which killed 22 people.
In a sharp attack upon May’s anti-terror credentials, Labour’s leader questioned why the police had faced dramatic cuts under her six-year tenure as home secretary and promised to recruit another 10,000 officers and 1,000 security service agents.
“You cannot protect the public on the cheap. The police and security services must get the resources they need, not 20,000 police cuts,” he said. “Theresa May was warned by the Police Federation but she accused them of ‘crying wolf’.”
Corbyn moved to quell fears that he would not authorise a shoot-to-kill policy after a 2015 interview clip from the BBC was used to cast doubts upon his use of the policy over recent weeks.
He told an audience in Carlisle: “I will take whatever action is necessary and effective to protect the security of our people and our country. That includes full authority for the police to use whatever force is necessary to protect and save life as they did last night.”
He took a further swipe at the Conservatives’ close alliance with Saudi Arabia and called for a clampdown on the funding of Islamist organisations in the UK.
“We do need to have some difficult conversations starting with Saudi Arabia and other Gulf states that have funded and fuelled extremist ideology,” he said.
Corbyn questioned why, as disclosed by Guardian, May had failed to publish a report commissioned by David Cameron into funding of jihadi groups which is thought to focus on Saudi Arabia.
The shadow foreign secretary, Emily Thornberry, said May’s statement on Sunday morning appeared to be a breach of an agreement with Labour to put aside political campaigning.
Thornberry told BBC Radio 4’s The World This Weekend that the statement was insensitive to the needs of those who were just becoming aware that their loved ones had died.
She said: “None of the things [May] is proposing in the four-point plan are immediate steps and so I regret the timing of this.
“I think that [what May has said] is drawing us into a debate. To come out on to the steps of 10 Downing Street immediately in the aftermath of a terrible outrage would not be something that would be expected. We need to do more but we also need to be sensitive to the fact that there are people who are only just discovering that their loved ones have died.”
May is expected to introduce control orders for terror suspects. Iain Duncan Smith, a former Tory work and pensions secretary, told The World this Weekend that she would probably try to toughen up terrorism, prevention and investigation measures, known as Tpims.
These are the measures introduced by the coalition to place restrictions on people who are suspected of being terrorists but who have not been convicted of an offence.
Duncan Smith said: “One of the things that I was concerned about in coalition [government] – I know Theresa May was when she was home secretary – was during the coalition the Tpim order that we brought in, which gives those powers, was watered down. And I think it was weakened too much.”
The former independent reviewer of terrorism legislation, Lord Carlile of Berriew, predicted that the first item on the agenda in any review would be the reintroduction – possibly under a new name – of control orders, which were replaced by the less stringent Tpims in 2011.
There were few clues in the Conservative manifesto about any new powers which may be offered to the police or security agencies. It stated that a Tory government would “continue to invest in our world-leading security services and maintain and develop our counter-terrorism strategy to protect us from terrorism at home and abroad”.