In a statement, the relatives urged the captors to end their "torment" of being separated from "ordinary family men" who were merely trying to earn a living.

The five have now been missing for more than 100 days since they were seized by armed men at the Iraqi finance ministry in Baghdad.

The statement said: "They are sons, fathers and brothers who were working to support us - their families. We miss them so much and want them to come home to us so that our families can be complete again and our children no longer have to endure the pain of missing their fathers."

The seized Britons are believed to be four security guards who were working for a private firm and a financial expert who was advising the Iraqi government. They have not been named.

"We appeal from our hearts to those who are holding our loved ones," the families said.

"These are not men with political views or any authority, they are ordinary family men who have parents, wives and children that love and cherish them - please send them home to us."

Foreign Secretary David Miliband expressed "deep concern" about the fate of the men, who are widely thought to have been seized by a Shiite group linked to radical cleric Moqtada al-Sadr. "I remain deeply concerned about the five British men taken in Iraq in May. They and their families have already endured over 100 days of anguish," Mr Miliband said.

US commanders said earlier this week that they believed the Britons were still alive.

Mr Miliband continued: "Since the men were taken, their families have had no definitive news of what has happened to their relatives. We will continue to do all we can for them. Taking hostages is never justified, no matter what cause it may claim to serve. The five men should be released immediately and returned to their loved ones."