The bombing campaign against Isis is set to last for “at least” three years, the Defence Secretary has said.

Michael Fallon said the campaign in Syria was “not going to be quick” and that American defiance chiefs had estimated planes could be dropping bombs well into 2017.

“The American estimate of the campaign in Iraq, which began last year, was that it would last at least three years and we’re not halfway through that yet,” he told BBC Radio 4’s Today programme.

“The operations there by the coalition have lasted just over a year and the Prime Minister has been pretty clear that this is going to be a long campaign to ensure that Daesh are thrown out of Iraq and that they are degraded and defeated in eastern Syria. This is not going to be quick.”

Mr Fallon said it would not be right for the UK to leave the bombing to other airforces, echoing earlier comments that Britain should not “outsource” its security.

He added that it would not be “likely” that Western ground troops would take part in the conflict because it would “radicalise the Sunni tribes even more”.

Defence Secretary Michael Fallon (Getty) (Stuart C. Wilson/Getty Images)

British warplanes launched their first air strikes last last night against Isis militants in Syria hafter Parliament authorised an extension of bombing to the country.

Four RAF Tornado jets took off from RAF Akrotiri in Cyprus, equipped with a combination of 500lb Paveway bombs and Raptor survellience pods, according to a BBC correspondent on the ground.

UK jets had already been bombing Isis targets in Iraq since last year and US, French, and allied jets had already been bombing targets in Syria.