The organisation provided vouchers for cat desexing at its shelters for concession card holders, saving them between $150 and $200 for the procedure.

The initiative was supported by state government grants that followed the introduction of the state's Cat Management Act in 2012.

The state funds have now run out, but RSPCA general manager Peter West said there were still 75 vouchers available at the Mowbray shelter through support from the Launceston City Council.

He said volunteers continued to support the initiative through regular fund-raising in an attempt to keep the program going.

``The best way we can get the cat population under control in Tasmania is by ensuring people desex their cats, and this initiative has made positive steps towards this goal,'' Mr West said.

``Anecdotal evidence from all our care centres tell us pregnant cats and unwanted litters are frequently abandoned by owners who have not taken the responsibility of owning a cat seriously.

``With fewer cats reproducing, there will be a reduced risk to wildlife.''

He said while the act states that cats must be desexed, there is no punitive measure to enforce it.

``We will continue to talk to the department and investigate ways that the Cat Management Act can be bolstered,'' Mr West said.

There are more than 150 cats at the shelter at the moment, of which 40 are in temporary foster care arrangements.

Each cat is desexed, microchipped, and ready for adoption.