Police Minister Rob Johnson has requested a security review of every WA police site after an 18-year-old man posed as a police officer at the Perth lock-up.

The teenager allegedly stole a police uniform and gained access undetected to the watch house in East Perth on a number of occasions.

He showed up at the lock-up in uniform with a full police utility belt, complete with handcuffs, police issue baton and holster, allegedly all stolen.

Police say he also had a replica firearm.

The ABC understands the watch house was not the only facility the imposter entered.

It is believed he also managed to get into Curtin House - where senior detectives from the serious and organised crime squads, and the police armoury, are based.

Police have refused to answer questions since the story broke but have released a statement saying they are investigating whether the teenager was assisted by a 25-year-old man who worked as a custody officer.

He has been stood down while internal affairs investigates any links between the two.

Opposition police spokeswoman, Michelle Roberts, says the matter should be investigated by the Corruption and Crime Commission.

"The most serious of criminals are housed in our lock-ups," she said.

"In recent weeks, the likes of Brett Masten and other serious criminals have been housed at the Perth lock-up, security there is of utmost importance, there are a lot of questions to be answered."

Security review

Mr Johnson says he has met senior police and requested a full review of security at every WA police site.

In a statement, the Minister said the breach is unacceptable and steps would be taken to ensure such an incident is not repeated.

Former deputy police commissioner, Murray Lampard, who is now a professor at Edith Cowan University, says it is a serious incident.

The man posed as a police officer at the watch house. ( ABC News )

"Police would certainly be very embarrassed about this breach of security," he said.

"It's something that they need to look at very seriously and certainly fix immediately, but it's a very serious matter for public confidence."

Professor Lampard says it is not known if the impostor was involved in any arrests.

"It's feasible to assume that certainly he would have had some access to prisoners," he said.

"Hopefully he would not have had access to confidential lock-up records, being a younger officer; that's certainly in the gambit of the more senior officers.

"You know, it just appears that the police have been very lucky that nothing serious has, as far as we believe, come out of this."

Police say it does not appear that the impersonator had direct contact with prisoners or was able to access police computers while he was in the building.

They also say the man was not on roster at the watch house.

The Police Union's Denis Hayden is seeking assurances no officers' personal details have been compromised.

"I believe that they've got a right to feel very, very insecure," he said.

"If he's accessed them in any way I've got serious concerns about our own people's security."

'Serious breach'

Ms Roberts says the questions should be answered immediately to give the public reassurance.

"This is one of the most serious breaches of police security that I can certainly remember," she said.

"It’s something highly unusual and I think it has shocked a lot of people in the community that someone could impersonate a police officer and have access to our lock-up.

"But not just have access, to actually don a police uniform and to work shifts or parts of shifts; now this is nothing short of amazing.

"We need to know exactly what access over what period of time."

The man who posed as a police officer has been charged with burglary, stealing, trespass and ten counts of impersonating a police officer.

He is due to appear in the Perth Magistrates Court on June 20.