Cameron says he is prepared to use nuclear weapons if necessary

The Prime Minister has said he is prepared to press the red button if he has to, as he looked to exploit Labour's division on the nation's security.

On the first day of the Conservative Party Conference in Manchester, David Cameron said he believed the country should retain the Trident nuclear deterrent.

And he said that Labour leader Jeremy Corbyn's recent comment that he would not authorise the use of nuclear weapons even if Britain was under nuclear attack "undermined national security".

Mr Cameron said: "The problem with his answer is, if you ... believe like me that Britain should keep the ultimate insurance policy of an independent nuclear deterrent, you have to accept there are circumstances in which its use would be justified.

"If you give any other answer then you are, frankly, undermining our national security, undermining our deterrent, " he told BBC1's Andrew Marr Show.

Mr Corbyn's remarks in an interview marred the last day of the Labour Party Conference.

The party is significantly divided on the issue with a number of prominent Shadow Cabinet members seeking to retain the Trident system - which is up for renewal next year - and Mr Corbyn suggesting he was happy to accept a split on the issue.

Security is one of the three key themes of the Conservative conference - the others are stability and opportunity - and Mr Cameron will be seeking to capitalise on Labour's division on the country's defence capabilities.

Mr Cameron also confirmed there would be a vote on British military action in Syria - despite Russia's recent intervention.

In a separate newspaper interview, he disclosed he would "beef up" the SAS and the number of drones Britain has to tackle Islamic State.

Mr Cameron told The Sunday Telegraph, the Ministry of Defence would buy a fleet of 20 Protector drones from the US.

On Saturday, Mr Cameron said Russian strikes in Syria were hitting citizens and helping the "butcher Bashar al Assad".

He said that few of the strikes were hitting IS targets. Defence Secretary Michael Fallon has said only one in 20 attacks have hit the terrorists.

The Prime Minister urged Russia's president Vladimir Putin to work with Europe and the US to fight IS and not to prop up the Assad regime.

Mr Fallon and Foreign Secretary Philip Hammond will both speak at the conference on Sunday.

(Sky News)