The rise to 350 animals in RSPCA care followed seizures of 300 from three properties, including 132 from one in Maylands.
The shelter has a normal capacity of 170 animals.
Pending court action has exacerbated the problem because animlas cannot be de-sexed or micro-chipped during this period, and cannot be re-homed.
Chief executive David van Ooran said the shelter was unable to house new cat arrivals and the society needed help from the community to continue caring for sick and mistreated animals.
‘Ideally we would like a transportable facility that would house six staff, so that we can utilise current office space to accommodate animals,’ he said.
‘This is about giving the animals the most comfortable accommodation that we can find and that means relocating staff.’
Mr van Ooran said the organisation was looking for cat foster carers to ensure animals lived as comfortably as possible until permanent homes could be found for them.
It also hoped to find a business willing to donate a donga-style transportable.
The head of the shelter, Dr Julie Bellamy, isamong staff whose work space has been impacted.
Her shared office space was at present in the main administration building, which was far from ideal because she needed to work from the shelter.