The staff association for rank and file police officers has said there is a lack of clarity over plans to introduce privatisation into policing.
The Police Federation said it agrees with a report issued today by the Home Affairs Select Committee that calls on the Home Office to take responsibility for ensuring the public and stakeholders were aware of the process.
The committee found that the "costly joint procurement exercise" being undertaken by Surrey and West Midlands Police lacked clarity.
The MPs said they are "not convinced that the Forces fully understood, or were fully able to articulate the process they were undertaking".
"Different forces are doing different things," said Simon Reed from the Police Federation.
"Some of the bidding companies are unsure of the rules, are unsure what they are supposed to be doing and where their role finishes.
"We accept there are roles such as HR and payroll that are open to be done by private companies, but there are roles that must remain police roles."
Mr Reed said that there are "blurred lines from the Home Office" and concern that some private contractors may think they will be allowed to undertake patrol functions and enforcement.
"They need to know it is not about that - the tender documents are not clear enough.
"One of these companies said when they bid for military contracts they are very clear.
"With Surrey and West Midlands it was reported that there would be some patrol work, then it was denied, but the contractors thought that."
The committee said the Home Office must take responsibility for ensuring the public and stakeholders were aware of the process and to postpone the exercise until November’s elections for the new Police and Crime Commissioners.
"The privatisation of aspects of the police service began under the last government, however it is an area where forces should tread very carefully as some police functions simply cannot be outsourced," said committee chair Keith Vaz.
"The Home Office must ensure it knows what services local forces wish to contract out, before agreeing to allow expenditure of £5 million on what is little more than a fishing expedition."