Garda whistleblower Sergeant Maurice McCabe has taken sick leave from the force.
It is understood he has been subjected to a number of incidents of alleged harassment in recent weeks.
Fellow whistleblower John Wilson wants interim Garda Commissioner Noirin O'Sullivan to investigate the allegations at a more senior level.
"He went sick on Monday, that's my understanding and he has documented numerous instances of alleged harassment, particularly over the last month or so," said Wilson.
"Now you'll appreciate that I cannot really act as a spokesperson for Sergeant McCabe, but I believe that his situation is very serious and warrants urgent attention by the interim Garda Comissioner herself".
"I want her to take direct responsibility for this situation" he added.