The Prime Minister gave her warning prior to Saturday’s attack on London Bridge.
It came as a Survation poll of 1,049 adults suggested Labour is a mere one per cent behind the Tories on 39 per to 40 per cent.
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If this was the result on Thursday then Corbyn could be Prime Minister on Friday, propped up by a “coalition of chaos” of Lib Dem Remainers and SNP Scottish separatists, who all want to force Britain to stay in the EU and tear the country apart.
Jeremy Corbyn showed us all why he cannot be trusted with Britain’s future
The six polls published yesterday still gave Mrs May a comfortable seven point average lead of 43 per cent to Labour’s 36 per cent.
A ComRes poll of 2,038 voters, almost double the Survation sample, was more optimistic showing the Conservatives with a healthy 12 point advantage over Labour of 47 per cent to 35 per cent.
In an article in a Sunday newspaper, Mrs May warned of the catastrophic effects of a Corbyn government.
Theresa May accused Mr Corbyn of being 'waffling and weak' on Brexit and security
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The first duty of every Prime Minister is to defend and protect the nation, says Theresa May
Pointing to his woeful performance on Friday night’s Question Time where he refused to say whether he would press the nuclear button to defend Britain, she said: “Jeremy Corbyn showed us all why he cannot be trusted with Britain’s future.
“And he showed beyond doubt that he has no answers to the greatest challenges of our age.
“He was waffling and weak on leaving the EU, waffling and weak on the economy, waffling and weak on standing up to anti-Semitism in his own party.”
She went on: “Most worryingly, he was waffling and weak on keeping us safe.
“The first duty of every Prime Minister is to defend and protect the nation.
“He made it clear he would not use our Trident deterrent even if the UK was coming under nuclear attack.