London Mayor Sadiq Khan has waded into the row over police cuts, warning the Metropolitan Police is facing the loss of thousands of frontline officers under Tory plans.
Mr Khan said the force could lose as many as 12,800 officers, which would reduce its strength by 40%, making it harder to tackle the terrorism threat.
The Labour mayor said the Met had already had to make £600m of cuts since 2010 and is now facing £400m more.
He said: “Our city has suffered two awful terrorist attacks since I was elected as mayor – and we must do everything possible to stop there being any more.
“Police officers in our communities act as the eyes and ears of the security services, providing the intelligence and information that allow us to disrupt attempted terrorist attacks.
“Cuts on this scale would make it harder to foil future terrorist attacks on our city – and as the mayor of London I’m simply not willing to stand by and let that happen.”
Mr Khan’s comments will heap pressure on Theresa May, whose record as Home Secretary is under scrutiny in the wake of the terror attacks.
At the Home Office, Mrs May oversaw cuts of 20,000 officers despite warnings from the Police Federation, which she accused of “crying wolf”.
On Monday, Jeremy Corbyn called for her resignation over the issue, and former David Cameron aide Steve Hilton said Mrs May should take responsibility for the problems facing police forces.
But the Prime Minister repeatedly refused to say she was wrong to make the cuts while she was Home Secretary and insisted counter-terrorism budgets had been protected.
Despite her assurances, Home Office documents, highlighted by The Times newspaper, show reductions in funding to the Office for Security and Counter-Terrorism (OSCT).
The OSCT is responsible for terrorism strategy at home and abroad and liaises with the intelligence services and police.
Mr Khan has come under repeated criticism from Donald Trump over his handling of the terror attacks.
The President started his Twitter assault on the London Mayor on Sunday, misrepresenting comments Mr Khan had made urging the public not to be alarmed by an increased police presence.
When Mr Khan issued a statement saying he was too busy dealing with the aftermath of a terror attack to respond to the President’s comments, Mr Trump doubled down with a second insult.
Mrs May has said the President was “wrong” to criticise Mr Khan.
“I think Sadiq Khan is doing a good job and it’s wrong to say anything else – he’s doing a good job,” she said.