Liam Kelly made the comments in a speech he delivered at the federation’s 54th annual conference.
He also attacked the “rush to criticise” officers, with some politicians only to be heard “bemoaning, criticising and condemning” the police, and complained of “half-hearted” backing for the police from some quarters (though he did not mention any parties by name),
Mr Kelly, in a copy of the speech shared with the press in advance of his address, said: “Of course, the service could have more from a Catholic background in its ranks, but if there’s an indifferent political approach taken by some parties, combined with community opposition and a terrorist threat to those who take the brave decision, it’s little wonder there’s a reluctance to raise heads above the parapet and come forward."
At present, about 67% of officers are “perceived Protestant” and 31% “perceived Catholic”.
To re-introduce 50-50 would "be an arbitrary and rather crude attempt at social engineering” that would foster “understandable resentment”, said Mr Kelly.
“The merit principle must prevail in favour of something that would build in bias and one-sidedness,” he said.
“There regrettably remains an unhealthy focus on the religious background of our officers that is not replicated in any other sector.
“In line with all other public services, our officers should be selected on the basis of their skills and attributes to do the difficult job.
“Their religious background is not only irrelevant to them but also to the public when they are responding to calls for help and service.”
Mr Kelly said he is “bluntly" making the call for people to do “their bit in a more vocal and assertive way to promote a career in policing”.
"Too often, there’s a rush to criticise, but when it comes to giving wholehearted encouragement and unequivocal endorsement of a career in policing, quite a few usually vocal spokespeople develop a case of laryngitis,” he said.
He added that some can “only be heard when bemoaning, criticising and condemning”, and should “take the principled step to end half-hearted support for policing; it’s time for all of them to get off the fence”.
Mr Kelly also went on to say: “Devolution was meant to be a boost, a better way of delivering accountable government.
"In our experience, instead of being a positive step, it has been disastrous.”
That is because “policing has struggled to make it on to the agenda” in the Executive “in any meaningful way,” whilst Westminster has “washed its hands” of the issue of policing.
He spoke about policing numbers, saying that in November 2001 there were around 7,500 full-time officers serving a population of 1.69 million people, but “today, with a population now exceeding 1.93 million, the actual number of officers disgracefully stands at 6,315” (and that “when you remove student officers from this total, the figure slides down towards 6,000”).
Mr Kelly also said that the legacy of the Troubles “continues to be a millstone” around the force’s neck, and that the total bill for handling historic cases “could top £875m, with a significant amount of that expected to be going into the coffers of legal firms”.
On the exit of Marie Anderson as Police Ombudsman, he said “it is no secret we had a difficult, tense relationship, specifically with her, and we eagerly await the appointment of her successor to see if those burnt bridges can be rebuilt”.
He also praised the BBC’s recent documentary Peelers for showing the danger which officers face, and made reference to the justice minister’s plans to introduce legislation “to provide for higher sentences for assaults on any person who is providing services to the public”.
Mr Kelly criticised the idea of “amalgamating our officers into a wider group of public-facing workers,” adding: “All assaults are wrong but, with the greatest respect, we strongly feel that an assault on, for example, a retail security guard, cannot on any level be legally assessed of being equated with attacking a police officer doing their duty.”