Quoting the two witnesses, the National Union of Journalists in the Philippines (NUJP) said they have been receiving death threats and "are now living in constant fear for their lives."
The NUJP said Damalerios widow, Gemma, and their only child have been in hiding since the murder. "But according to Gemma herself, unidentified men in vehicles and motorcycles without (license) plates have been seen casing their house during the past weeks," it said in a statement.
The threats and harassment, according to the NUJP, heightened after the Department of Justice (DOJ) removed Damalerios wife and child and the two witnesses from the witness protection program.
The journalists group quoted Gemma and one of the witnesses as saying that the DOJ dropped them at the start of this year "supposedly after the (department) ruled that all archived cases should be removed from the program."
The NUJP said it views these developments "with utmost alarm and concern," adding that it fears for the safety of Damalerios family and the witnesses.
"The governments seeming disinterest in pursuing the Damalerio case will ensure that justice will not be done and the killers and masterminds of the murder will remain scot-free," it said.
"The failure of the government to seriously pursue this case will only encourage future killings of Filipino journalists," it added.
The NUJP dared Malacañang and the Philippine National Police to arrest Damalerios alleged killer, PO1 Guillermo Wapile, who is reportedly "seen around (Pagadian City) and in nearby areas."
"If everybody else knows where Wapile is, it is impossible for the police not to know the same thing. We are wondering why the authorities cannot arrest Wapile," the group said.
If anything happens to Damalerios family and the two witnesses, the NUJP said it will hold accountable Malacañang, the PNP, the DOJ and the Task Force Newsmen which Deputy Director General Edgar Aglipay, the newly installed PNP chief, created last Aug. 16.
The NUJP statement was signed by Mindanao-based Carlos Conde, the groups secretary-general and a Philippine correspondent of the New York Times.
At least five journalists have been killed since January this year and 55 since democracy was restored in 1986 with the fall of the Marcos dictatorship.