Hammer attack on WA Premier's office

The office of West Australian Premier Colin Barnett has been attacked by a hammer-wielding vandal, who daubed "Egomaniac" in red across the building's windows.

Mr Barnett, who has recently been the subject of vitriolic criticism over his policy to cull large sharks in WA waters, was not in the office at the time.

He is still on annual leave, a spokeswoman from his office said.

A 29-year-old man is in custody on suspicion of smashing the front windows, but no charges have been laid as yet.

Police are still investigating at the scene.