Prime Minister Gordon Brown has demanded the immediate release of five Britons being held hostage in Iraq.
He promised the Government would do "everything in our power" to secure the freedom of the four security guards and one computer expert who were kidnapped in Baghdad in May.
Their abductors recently released a video of one of the men, threatening to kill the captives unless British troops withdrew from the country.
Mr Brown said in a statement: "They will not change our policy in any way." He added: "We are demanding the immediate release" of the hostages.
The Prime Minister said: "My first thoughts are with the five hostages and with their families, who have endured an enormous amount over these last six months, and I want to thank them for their bravery and their resilience.
"We will do everything in our power to secure our objective, which is the immediate release of the hostages."
Mr Brown thanked Iraqi premier Nouri Maliki and his government for their efforts so far in trying to secure the hostages' freedom and added: "We will give them our full support."
Mr Brown went on: "The taking of hostages is completely unjustified, wholly unacceptable and we are making it clear they will not change our policy in any way."
He added that policy in any case "has been to move from combat to overwatch" in southern Iraq.
Mr Brown added: "I want the hostage takers to accept their responsibility, to understand the consequences of what they are doing, to make possible the immediate release of the hostages, to allow them to come home at the earliest opportunity."
