Some 72 Catholic recruits have quit the PSNI, citing a range of reasons for dropping out, including work difficulties and republican paramilitary threats.
Catholic representation has risen to 1,574 officers under new 50/50 recruitment policies - 20 per cent of manpower.
Jane Winter, from the British/Irish Rights Watch pressure group, claimed the figure of 72 Catholic drop-outs damaged community confidence in the force.
“The PSNI have not been able to recruit enough Catholic police officers to the force; this is undermining the Patten recommendations and community confidence in the police,” Ms Winter said.
“This failure is in part due to failings within the PSNI such as an absence of minority representation and partly to external factors such as the intimidation of new recruits.
“These are the sort of teething problems we would expect given the campaign that there’s been on the part of republican dissidents to dissuade people from joining.”
Some members of District Policing Partnerships -- boards which monitor policing performance across the North -- have been subject to intimidation.
Sinn Féin does not sit on the new policing structures but may yield to pressure to endorse them to allow a return to power-sharing government.
Meanwhile, President Mary McAleese has revealed she has relatives who joined the police service.
“We have seen members of the PSNI gaelic football team, on which I have members of my own family [and clan] coming down and playing with members of the Garda Siochana,” she said.