David Cameron has insisted the West and its allies needed to "crush" Isil in Iraq and Syria following the Tunisian terrorist attack that claimed 38 lives.

The Prime Minister insisted Britain will prevail in its generational struggle against extremism as it is feared around 30 British holidaymakers, including four Scots, may have died in the beach gun attack in the resort of Sousse.

Mr Cameron said the country had to "confront this evil with everything we have got".

He told MPs Isil had hijacked the Islamic faith for its own perverted ends and the UK and its allies had to challenge and defeat its extremist narrative.

"Just as in the Cold War, we did have to confront the ideology; we have to do so again. In the end, we will win because our values of democracy, tolerance, the rule of law, freedom and free enterprise are better values and offer young people far more hope than going off and being part of a death cult that subjugates women, murders homosexuals and creates such murder and mayhem across the world," declared Mr Cameron.

He argued that there had to be a "full-spectrum response" to the latest atrocity, which has claimed as many as 30 British lives killed by Seifeddine Rezgui, 23, who went on the rampage on a beach on Friday armed with an automatic weapon.

The victims include James and Ann McQuire, from Cumbernauld, North Lanarkshire, while the family of Billy and Lisa Graham, from Perth, are still waiting for news of their loved ones.

Others who died included Carly Lovett, 24, from Gainsborough, Lincolnshire, who was a graduate of Lincoln University and a beauty blogger, Lisa Burbidge, in her 60s, from Gateshead, and Claire Windass, 54, from Hull.

Britain is currently engaged directly in airstrikes in Iraq but not in Syria. Downing Street, asked if consideration could be given to extending direct military action to Syria, said if the UK Government were to look to do this, then "we would return to Parliament".

The PM pointed to new measures to tackle extremism and referred to a new Bill to combat Isil's use of modern technology like the Internet. However, he did not elaborate on the details.

US President Barack Obama called the Prime Minister to express his condolences over the loss of British life in Tunisia. A No 10 spokesman said he told him the "United States stood firmly by the UK during this difficult time."

Home Secretary Theresa May condemned the "despicable act of cruelty" after she visited the scene of the attacks to lay flowers.

, she said: "How could a place of such beauty, of relaxation and happiness, be turned into such a scene of brutality and destruction?"

She said she had heard "horror stories" of those caught up in the attack and accounts of "great bravery", including Mathew James, who was hit in the hip, chest and pelvis as he shielded wife-to-be Saera Wilson from gunfire.

Mrs May held talks with Tunisian, German, French and Belgian ministers on addressing the threat posed by IS.

"We are very clear that the terrorists will not win. We will be united in working together to defeat them, but united also in working to defend our values," she said.

All British nationals injured in the terror attack on a Tunisian beach will be returned to the UK for treatment within the next 24 hours. The official British death toll is now at 18.

Earlier, Mr Cameron chaired a Whitehall meeting of the Cobra emergency committee, attended by senior Ministers, representatives from the security services and the Metropolitan Police. John Swinney, the Deputy First Minister, took part via video-link. In Edinburgh, First Minister Nicola Sturgeon chaired a meeting of the Scottish Government's Resilience Committee.

Ahead of the Commons statement, MPs rose to observe a minute's silence. The PM said there would be a national minute's silence on Friday at noon; precisely a week after the terror attack at the hotel in Sousse. A "fitting memorial" to the victims would also be arranged in liaison with the families.

Mr Cameron went through the details of the investigation thus far and explained that while the terrorist was thought to be a lone gunman, he might have been part of a wider Isil network with accomplices. The Tunisian authorities, helped by British police, were continuing with their enquiries.

Some eyebrows were raised about how the Foreign Office was not advising against Britons travelling to the coast of Tunisia.

Stuart McDonald, the MP for Cumbernauld, related the shock felt by the local community at the deaths of James and Ann McQuire in the tragedy, but asked what reassurances could be given about the reliability of Foreign Office travel advice.

The PM, who expressed his condolences to the McQuire family and friends, said travel advice was based on fine judgements like intelligence and the capacity of the Tunisian system; at present, it was not against travel to the coastal regions of Tunisia.

"These are difficult decisions," admitted Mr Cameron but stressed: " We mustn't be cowed by the terrorists. They want us to basically wipe out the Tunisian tourism industry, which is 15 per cent of their economy. The decision we take puts the safety of British first and foremost; if the evidence changes, we would change our advice."

For Labour, Harriet Harman said MPs were meeting in "dark times" and urged the UK Government to set up a dedicated taskforce to help those bereaved and injured.

Angus Robertson, the SNP leader, denounced the "horrific" attack but asked if the time had not come for the English-speaking world to "stop using Islamic State, Isis or Isil and that instead we and our media should use Daesh, the commonly used term across the Middle East?"

Mr Cameron agreed, saying the use of Islamic State was "particularly offensive to many Muslims" given it was not a state but a barbaric regime of terrorism and oppression.

Suspected associates of the Tunisian beach gunman have been arrested. Rezgui was shot dead by security forces.

His father said that his son had been brain-washed by Isil.

Hakim Rezgui said he 'did not have any answers' about why he would have committed 'such a horror.'