UPDATE: A man has been charged after the Premier's electoral office was vandalised this afternoon.
Several windows and a glass door were smashed and graffiti sprayed at Colin Barnett's Cottesloe office.
Police arrested a 29-year-old Parmelia man over the incident involving a hammer and spray paint.
He has been charged with two counts of criminal damage.
The word "egomaniac" was sprayed in red paint across the building's windows.
Mr Barnett, who is on annual leave, was not in the Stirling Highway office at the time, a spokeswoman said.
Police are investigating the incident, which happened at 2pm.
Nearby business owners said they were stunned by the attack.
Police including detectives and forensics officers attended the scene and officers also searched a car at Cottesloe train station.
The Parmelia man has been released on bail and is expected to appear in Perth Magistrate's Court on January 21.
The attack in broad daylight has sparked calls for increased security at the strata building where more than 60 people work.
People who work in offices in the building said this was the worst attack they had ever seen.
"We have had some protests but never something so destructive," one person said.
The office block's body corporate chairman Rob Towner called for extra security measures.
"It is time for increased security for the Premier and, more importantly, for his staff," he said.