In an interview with NBC about tackling extremism and Islamic State in particular, David Cameron said, 'I want Britain to do more and we are talking about that now – but we must win support from our MPs.' REUTERS

Britain will step up its efforts to target Islamic State (Isis) targets and join the US to destroy the caliphate set up by IS militants, said the prime minister of UK.

In his interview with US television NBC, David Cameron said the UK would help to hammer the IS in Iraq and help the US in Syria, but only after winning the approval of his MPs.

"I want Britain to do more. I'll always have to take my parliament with me," Cameron told NBC

"We're talking and discussing at the moment, including with the opposition parties in Britain, what more we can do. But be in no doubt, we're committed to working with you to destroy the caliphate in both countries."

Labour interim leader Harriet Harman was invited to a National Security Council briefing last week, believed to be a sign that the government is seeking to build cross-party parliamentary support for operations in Syria.

Cameron's promise follows outrage and an opposition demand for an explanation on Saturday when it emerged that RAF pilots had taken part in bombing raids over Syria.

Last week, it was revealed that UK warplanes had launched missions against Isis in Syria, despite MPs voting to block involvement in the Syrian civil war in 2013. Parliament has approved UK airstrikes against Isis in Iraq.

Downing Street confirmed that the Prime Minister was aware that RAF aircrews had taken part in Syria bombing missions, alongside US and Canadian crews.

In the interview, Camron added. "We've already carried out more air strikes in Iraq than anyone else other than the United States.

"But I want us to step up and do more, what I call a full-spectrum response. That means hammering ISIL in Iraq and helping with the work you're doing in Syria.

"Be in no doubt, we're committed to working with you to destroy the caliphate in both countries," he said.

'Cannon fodder' warning

In a speech on Monday at Birmingham, the prime minister is expected to warn young Britons against joining IS and ending up as "cannon fodder".

"If you are a boy, they will brainwash you, strap bombs to your body and blow you up. If you are a girl, they will enslave and abuse you. That is the sick and brutal reality of Isil," he will say.

More than 700 men and women and teenagers have travelled from Britain to Iraq and Syria to join the IS and half of them have returned home disillusioned.

The prime minister had called upon Muslims to do more within their communities and counter the dangers posed by those who "quietly condone" IS militants' extremism.

Cameron is expected to endorse British values while condemning the brutal jihad of the extremists.

He will refer to Britain's liberal values to be used to deglamorise extremism. "We should expose their extremism for what it is – a belief system that glorifies violence and subjugates its people… not least Muslim people."

The prime minister will urge moderate Muslims to reject anti-Western conspiracy theories and call on everyone living in Britain to stand up for British values.

"We believe in freedom of speech, freedom of worship, equal rights regardless of race, sex, sexuality or faith. We respect different faiths but expect those faiths to support the British way of life."

He is expected to unveil a range of measures in a five-year plan to crack down on Islamic extremism, including closure of mosques associated with extremists, a review of sharia courts, and a new law to prohibit hate preaching in public or online.