Junior Minister Ian Paisley jnr attacked Assembly member last night John Dallat for making "wild allegations" over the RUC handling of the Greysteel massacre.
The DUP MLA said Mr Dallat should be "more circumspect" after the Police Ombudsman did not uphold a complaint claiming police could have prevented the 1993 Halloween killings.
Mr Dallat complained that he had given the RUC information that could have prevented the UDA attack at the Rising Sun Bar, which left eight people dead.
But Ombudsman Nuala O'Loan found that police had taken "appropriate action" with information provided by Mr Dallat.
She said she could find no evidence that the RUC had information that could have prevented the attacks.
Mrs O'Loan also rejected suggestions that UDA killer Torrens Knight was protected by police.
Mr Paisley said: "This whole sorry episode serves to highlight the need for elected representatives to act responsibly.
"Wild allegations can be deeply damaging to community confidence in policing. The reputation of individual officers has been besmirched, not to mention the impact on the relatives of the victims."
But earlier Mr Dallat defended his position. "I don't regret bringing the complaint to the Ombudsman. It was based on what I believe was important, useful information," he said.
"I still believe a lot greater effort should have been put into dealing with that gang."
Mr Dallat added: "I was playing the role of a public representative who had people coming to me with information which was valuable.
" I believe she was severely hampered by the lack of a paper trail.
" As a civilian looking in on it, I have no doubt that a lot more could have been done and, if it was today, it would have been done."