Iraq-born Tory MP Nadhim Zahawi has said that local leaders in northern Iraq estimate that between 500 and 700 Britons are fighting with the Islamist militants.
He told Channel 4 News that he was seeking further information after a high-ranking official told him one had been found "with a Liverpool Football Club membership card" and another carrying a different UK-related membership card.
Solicitor Simon McKay is representing four of the six families of military policemen who died in Iraq in 2003. He talks about claims of new evidence coming to light that could prompt a fresh inquest into the deaths.
A ITV documentary has followed the daughter of ITV News war reporter Terry Lloyd as she retraces his final steps in Iraq as part of her deeply personal search for the truth about the circumstances surrounding his death.
Terry was killed in southern Iraq ten years ago, along with cameraman Frederic Nerac and translator Hussein Osman, after their convoy came under attack by the US Army.
Cameraman Daniel Demoustier - who was driving the vehicle carrying Terry when they were initially fired upon - survived.
Chelsey Lloyd has returned to where he was shot dead, along with Daniel and presenter Mark Austin, who was also in the country covering the start of the war.
“I need an understanding of what happened that day because I wasn’t there and because it was so far away," she said.
"I need to piece together the events of those days to create a kind of timeline, a picture in my head, to help me.”
Who Killed My Dad? The Death of Terry Lloyd is on ITV at 10.35pm tonight.
The mother of a British military policeman killed by a mob in Iraq has launched High Court action in an attempt to force the Ministry of Defence to hold a public inquiry.
Pat Long is seeking a judicial review of Defence Secretary Philip Hammond's refusal to hold the inquiry.
Lance Corporal Tom Keys from Solihull and Corporal Russell Aston from Swadlincote in Derbyshire were part of a group of six Redcaps killed after Iraqis attacked a police station in Southern Iraq in June 2003.
An inquest into the six deaths recorded a narrative verdict of unlawful killing, and said the soldiers should have been better equipped.
Lawyers say a hearing is unlikely to take place until the autumn.