Murdered aid worker Margaret Hassan was killed in Iraq because the UK government refused to speak to her hostage-takers, her family has claimed.
Margaret Hassan had lived in Iraq for 30 years and married an Iraqi
Mrs Hassan, who had British, Iraqi and Irish nationality, was taken in October 2004. Her body has not been found.
Her family said kidnappers made four calls to her Iraqi husband Tahseen asking to speak to the British Embassy.
The Foreign Office confirmed he was called from her phone, but could not verify the caller's kidnapping claims.
The government has also said it had wanted to "minimise" Mrs Hassan's UK links.
Three on trial
Three men are due to go on trial in Baghdad on Monday for the killing of the Care International worker - who was born in Dublin but had lived in Iraq for 30 years.
Deidre, Geraldine, Kathryn and Michael Fitzsimons said in a statement they had begged foreign secretaries Jack Straw and Margaret Beckett, as well as the Foreign Office, to arrange for the men - who were arrested by the US military - to be interviewed by British Military Police.
"They have refused this request even though this is the only way that Margaret's remains will be found and we can bring her home to be buried with the dignity she deserves," they said in a statement.
"We believe the time has now come for the British and Irish people to know the truth of what happened to our sister Margaret, a British subject.
"During the period of her captivity, four calls were made from the kidnappers to her husband Tahseen in Baghdad.
"These calls were made from Margaret's mobile phone.
"The hostage-takers demanded to speak to a member of the British Embassy, but Tahseen had been told by the British that they would not speak to the kidnappers.
"We believe that the refusal by the British government to open a dialogue with the kidnappers cost our sister her life.
"Margaret, who was vocally opposed to the war in Iraq, was sacrificed for the political ends of Tony Blair and George Bush."
The Foreign Office said: "Our strategy was one of personalisation and localisation - to minimise the links between Margaret Hassan and the UK."
A spokesman said he understood her family had criticisms of the government's approach, but they remained in constant contact with them, he added.