Extra powers for police community support officers are being rolled out across Sussex.
PCSOs in Brighton and Hove are among the first to be given new powers to detain people suspected of a crime for up to half an hour.
However, the civilian officers will only be able to hold members of the public until a police officer arrives if they agree.
PCSOs in every part of Sussex have been granted the new powers by the force’s chief constable and will be trained during their usual training sessions. Officers in Brighton and Hove have already started using the new powers.
The changes to the civilian officers’ powers have raised concerns among civil liberty campaigners.
Josie Appleton from campaign group the Manifesto Club said: “This is a very concerning development which has worrying implications for civil liberties.
“PCSOs are already responsible for some very erratic and meddling behaviour, and this will become worse if they are given more powers of search/detention.”
The Police Federation, which represents rank and file officers, said they were concerned the changes could result in PCSOs filling in for cuts in the numbers of police officers.
Sussex Police Federation chairman Bob Brown said: “We support any measure that helps police officers carry out their jobs.
“PCSOs play a valuable role in intelligence gathering and provide a valuable support role for police.
“But these powers will only work with people who are compliant. What we really want to see are more police on our streets and not the cutbacks we have seen in recent years.”
Sussex community support officers have been given the new power to detain suspects under the Police Reform Act 2002.
They have not been given the power to use force, but if a person fails to supply their name and address or makes off, it is an offence they can be arrested for later.
They have also been given the power to issue fixed penalty notices for disorder and dog fouling, disperse groups and order people under 16 to go home, and search for alcohol and tobacco.
Assistant chief constable Robin Merrett said: “PCSOs will have greater discretion and flexibility to deal with things within their neighbourhoods, which matter most to their communities.”