The Isis militant group is not being pushed back in Syria despite the extension of British air strikes to the country, ministers have admitted.

Defence Secretary Michael Fallon told MPs that the situation in the country was “complicated” and that recent events on the ground had concerned the Government.

“Daesh are being pushed back in Iraq, there’s no doubt about that – they’re being pushed up the Tigris and they’re being pushed back West along the Euphrates,” he told MPs in the House of Commons when asked about the situation there.

“In Syria the position is much more complicated and we are concerned at some of the more recent reports that may suggest coordination between Syrian democratic forces and the Assad regime, which is not helpful to the long-term aim of defeating Daesh.”

Mr Fallon said Isis was “on the back foot in Iraq” but that “that is not happening yet in Syria and I ... am extremely concerned about the proliferation of Daesh along the Libyan coastline”.

The secretary of state however said the UK was playing possibly the second most important role in the coalition air campaign in Syria – and had ran 2,100 combat missions against the group and carried out 600 strikes.

Labour’s shadow defence minister Toby Perkins raised the issue of a reported Isis advancement against Kurdish fighters’ positions north of the city of Raqqa.

“Given that we were hoping the moderate forces were waiting to take the fight to Daesh this is of course concerning,” he suggested.

The SNP’s Westminster spokesperson for Defence issues Brendan O’Hara warned that a dramatic increase of Isis fighters in Libya suggested that air strikes in Syria were displacing the militant group rather than killing them.

In pictures: Syria air strikes (2014) Show all 20 1 /20 In pictures: Syria air strikes (2014) In pictures: Syria air strikes (2014) Syria Syrian citizens check a damaged house that targeted by the coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Isis group, between the northern province of Aleppo and Idlib In pictures: Syria air strikes (2014) Syria A Syrian boy (L) looking at a destroyed car that activists say was targeted by the coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Islamic State group, between the northern province of Aleppo and Idlib In pictures: Syria air strikes (2014) Syria Parts of a missile that activists say was fired by coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Isis group, between the northern province of Aleppo and Idlib In pictures: Syria air strikes (2014) Syria Tthe guided-missile destroyer USS Arleigh Burke (DDG 51) launching Tomahawk cruise missiles against Isis targets In pictures: Syria air strikes (2014) Syria The USS Arleigh Burke (DDG 51) launches a Tomahawk cruise missiles in the Red Sea, to conduct strike missions against Isis group targets in Syria In pictures: Syria air strikes (2014) Syria The guided-missile cruiser USS Philippine Sea (CG 58) launching a Tomahawk cruise missile against Isis targets in Syria, as seen from the aircraft carrier USS George H.W. Bush (CVN 77) in the Arabian Gulf In pictures: Syria air strikes (2014) Syria US navy sailors standing watch on the bridge while Tomahawk cruise missiles are launched against Isis targets in Syria, aboard the guided-missile cruiser USS Philippine Sea (CG 58), in the Arabian Gulf In pictures: Syria air strikes (2014) Syria An F/A-18C Hornet, attached to Strike Fighter Squadron (VFA) 87 prepares to launch from the flight deck of the aircraft carrier USS George H.W. Bush (CVN 77) in the Arabian Gulf, to conduct strike missions against Isis group targets AFP/Robert Burck In pictures: Syria air strikes (2014) Syria The US-led airstrikes in Syria against Isis targets in and around the city of Raqqa In pictures: Syria air strikes (2014) Syria A fighter from the Isis group holds a piece of what the IS is saying is a US drone that crashed into a communications tower in the Syrian city of Raqqa In pictures: Syria air strikes (2014) Syria Fighters from the Isis organisation pray at the spot where the jihadist group said a US drone crashed into a communications tower in the Syrian city of Raqqa In pictures: Syria air strikes (2014) Syria Fighters from the Isis group load a van with parts that they said was a US drone that crashed into a communications tower in the Syrian city of Raqqa In pictures: Syria air strikes (2014) Syria Fighters from the Isis group load a van with parts that they said was a US drone that crashed into a communications tower in Raqqa In pictures: Syria air strikes (2014) Syria Fighters from the Isis group gesture as they load a van with parts that they said was a US drone that crashed into a communications tower in Raqqa. A US-led coalition on carried out its first air strikes and missile attacks against jihadist positions in Syria, with Damascus saying it had been informed by Washington before the operation began In pictures: Syria air strikes (2014) Syria A Syrian man rides his bike past a communications tower that was destroyed after a US drone crashed into it, according to fighters with the Isis group, in the Syrian city of Raqqa In pictures: Syria air strikes (2014) Syria People inspect a shop damaged after what Isis militants say was a U.S. drone crashed into a communication station nearby in Raqqa In pictures: Syria air strikes (2014) Syria A man holds the remains of what Isis militants say was a U.S. drone which crashed in Raqqa In pictures: Syria air strikes (2014) Syria Resident gather in the back of a van the remains of what Isis militants say was a drone which crashed in Raqqa In pictures: Syria air strikes (2014) Syria A man inspects the remains of what Isismilitants say was a U.S. drone which crashed into a communication tower in Raqqa In pictures: Syria air strikes (2014) Syria A man inspects the remains of what Isis militants say was a U.S. drone which crashed in Raqqa

A freedom of information request by the Huffington Post UK website earlier this month found that only seven Isis fighters had been killed by British bombs, according to Ministry of Defence records.

Furthermore, the much vaunted Brimstone missiles, which David Cameron had pledged would “cut off the snake’s head” in Syria and ministers had dubbed “unique” – had killed no Isis fighters.

Labour leader Jeremy Corbyn opposed air strikes in Syria on the basis that they would amount to another “reckless, half-baked intervention”.

He argued that the Prime Minister had failed to explain why extended the bombing of Isis would make a significant difference to the campaign in Syria when the group was already being bombed by the United States, Russia, France, and other power.