Islamic State: Britain backs international pledge to use military action 'if necessary' against Isis

David Cameron expected to call for British air strikes after Scottish referendum

Britain has joined more than 20 other countries in a pledge to fight against the Islamic State (Isis) in Iraq using “any means necessary”, including military action.

Philip Hammond, the Foreign Secretary, backed the resolution following Monday’s international summit in Paris, bringing the UK closer to military intervention.

A statement jointly issued by delegates said they would support the new Iraqi government in its fight "by any means necessary, including appropriate military assistance, in line with the needs expressed by the Iraqi authorities, in accordance with international law and without jeopardising civilian security.”

The conference came little over a day after footage emerged of the brutal murder of British aid worker David Haines by the same group who beheaded American journalists James Foley and Steven Sotloff.

The masked British militant known as “jihadi John”, believed to have carried out all three murders, went on to threaten the life of a second British hostage, Alan Henning.

Mr Hammond told Sky News no decision had been made about how Britain will be involved but it would pay a “leading role” in the coalition against Isis.

Hammond was overruled after previously saying that Britain would not be taking part in air strikes in Syria

“We cannot be deterred from our strategic objective of crushing Isil and the barbaric ideology they are trying to impose on the region,” he added.

The Government has not ruled out British air strikes in Iraq or Syria and there have been reports that the Prime Minister will announce plans next week.

Calling the group the “embodiment of evil” following the release of footage showing his murder, the Prime Minister vowed to “hunt down those responsible and bring them to justice”.

Sources told the Telegraph that Mr Cameron was resisting pressure to recall Parliament this week and will wait until after the Scottish referendum on Thursday to pitch for air strikes.

He will outline plans to combat Isis at the UN General Assembly starting in New York on Tuesday and call MPs back to the Commons on Thursday, the paper reported.

David Cameron has vowed to 'hunt down' David Haines' killers

A Downing Street spokesperson quickly dismissed the reports as “speculation” but did not deny an announcement was being considered.

British Tornadoes and surveillance aircraft are currently in Iraq carrying out intelligence and logistics operations.

France and Australia have already committed military assistance following more than a month of US air strikes against Isis targets in Iraq.

Countries signing today’s pledge included several European and Asian nations, as well as Middle Eastern countries including Saudi Arabia, the United Arab Emirates, Kuwait and Oman.

The support of regional partners was a key aim of Britain and the US, who are attempting to avoid mistakes of the 2003 Iraq invasion by ensuring international co-operation.

At the start of the summit on Monday, President François Hollande told delegates that there was "no time to lose" fighting Isis.

"The terrorist threat is global and the response must be global," he added.

Still bruised from his Commons defeat last year where he failed to secure a vote approving military action against Bashar al-Assad’s regime in Syria, the Prime Minister is understood to be securing support for a new campaign.

The Liberal Democrats and Labour are believed to be reluctant to endorse air strikes in Syria, where military action could raise legal issues if carried out without the Government’s consent.

The Iraqi Government, by contrast, has called for international military aid to fight Isis, which now controls a third of the country.

Alan Henning at a refugee camp on the Syrian-Turkish border

Barack Obama has confirmed America’s commitment to “degrade and destroy” the group, which beheaded two US journalists before Mr Haines, and several Arab states including the United Arab Emirates and Saudi Arabia are reported to be answering John Kerry’s call for allies to join strikes.

Footage of Mr Haines being murdered, possibly by the same man known as “jihadi John” who beheaded James Foley and Steven Sotloff, emerged on Saturday night.

Mr Cameron described the aid worker, who had been working to establish refugee camps in Syria when he was kidnapped in March last year, as a “British hero”.

The 44-year-old, who grew up in Scotland, had two daughters and lived in Croatia with his wife Dragana.

On Friday, the Foreign Office released a statement from his family pleading for Isis to respond to their attempts to get in contact.

Mr Haines’ life had been threatened at the end of the video showing the murder of Steven Sotloff and in a similar pattern, Mr Henning was revealed at the end of the latest video.

The 47-year-old, a volunteer aid worker from Salford, was captured in December in an aid convoy near Syria’s border with Turkey.

Additional reporting by agencies