Northern Ireland's new Security Minister, Shaun Woodward, has denounced threats issued against the McCartney sisters. He said he took the developments "extremely seriously".
The family of Robert McCartney, who was beaten and stabbed to death outside a bar on January 30th, have been told by police of threats to burn them out of their homes.
Mr Woodward, recently appointed to the Northern Ireland Office as a junior minister, said: "I have huge respect for the members of that family and what they are trying to do, and intimidation, wherever it happens is a very, very bad thing."
He added: "I fully support the family in everything they are doing and I fully support what the police are doing and I encourage anybody in Northern Ireland to come forward and help." Mr Woodward's NIO colleague, Angela Smith, said the threats were "beneath contempt".
Blaming what they called "criminal elements", police officers told the five McCartney sisters and the murdered man's partner, Bridgeen Hagans, that their intelligence had uncovered a threat to have them burned out. PSNI headquarters declined to say yesterday if new protection measures were being put into place to protect the McCartney homes and the sandwich bar business of Donna McCartney.
A spokeswoman said the PSNI would not discuss individual security measures.
Catherine McCartney said the threats would not stop them in their search for justice and they openly questioned what the police meant by "criminal elements".
"We would like to know exactly what that means. Does that mean criminal elements from within a terrorist organisation?" Paula McCartney said they were taking the threats "very seriously" but they would not stop them bringing a civil action against their brother's alleged killers.
Earlier this week the European Parliament voted to back a civil action against those the family believe are responsible for their brother's death in the event of a failure to secure convictions in the courts.
"The civil action will go ahead as planned," she said. "And no, this will not deter us in any way." "At the end of the day, if they are intimidating the victims of the murder, what are they doing to the witnesses? The family has continued to question republican goodwill in relation to their quest for justice.
"How can Sinn Féin say that the intimidation of witnesses does not exist? It is completely ludicrous," said Paula McCartney.
Sinn Féin president Gerry Adams yesterday strongly denied republican involvement in the intimidation. He condemned those who were behind the threats. He also questioned the PSNI nvestigation into the case.
"I am confident that there are no threats to this family from republicans. The recent election results were a clear endorsement of Sinn Féin's stand in support of the family and we remain totally behind their objective of having the men responsible for the murder of Robert McCartney brought to court and held to account for their actions," he said.
Turning to the police investigation, he added: "In any other high-profile murder case, in any other city, I'm sure matters would have been investigated more thoroughly and with more urgency."
The IRA has expelled three members for their role in the stabbing and offered to the McCartney family to have other individuals shot.
The SDLP deputy leader, Alasdair McDonnell, condemned the threats and said Mr Adams could not "pass the buck" to the police.