Southern River MLA Peter Abetz is disappointed with the outcome of the State electorate changes.
The boundaries were finalised last month as part of the shuffle which saw changes made to 50 of the 59 electorates.
Most people will be affected with 87.5 per cent of electors residing in districts where boundaries have been altered.
The new boundaries will not apply until the next State election, on March 11, 2017.
Mr Abetz said he was disappointed because he wanted the Forest Lakes area of Thornlie in his area as he believed it had similar issues as those in Southern River and Canning Vale.
Instead, that area will remain with Gosnells MLA Chris Tallentire, who will be the member for the newly-named Thornlie.
It has been that way since 2008.
Mr Abetz said the issues faced in Southern River and Gosnells were vastly different.
“I needed the extra area as I lost a lot of Canning Vale to Jandakot and the Liberal Party made a submission for it to be the Forest Lakes area of Thornlie,” he said.