National security responsibility should not be devolved in its entirety from Westminster to Northern Ireland, the Police Federation has said.
Sinn Fein has questioned the need for a Northern Ireland Office following the transfer of most policing and justice powers from London to Belfast.
Secretary of State Owen Paterson still controls national security matters like deciding whether to withhold information at inquests.
Federation chairman Terry Spence said: "I am not convinced that we are ready to devolve such a fundamental responsibility, in its entirety, to Northern Ireland.
"Your position, sir, as regards this federation, is vital to enable us to serve the needs of the Northern Ireland community and is anything but superfluous."
Mr Spence separately criticised the Policing Board of politicians and independent members, which oversees the police, for allegedly leaking confidential information to their colleagues and the media.
He said: "The Board has not taken politics out of policing - on the contrary, it has provided politicians with endless opportunity to pursue narrow political advantage."
He said Mr Paterson has an essential role representing officers' views to cabinet colleagues.
"Our access to you means that we hope to inform your views when matters of dispute find their way on to the Cabinet agenda," Mr Spence said.
"The opportunity to brief you is a great comfort to us. While we may not always be aligned in our views, we are grateful that our voice is heard where it matters."