People resigning from a party should fully resign from parliament at the same time

First Shawn Crockwell, now Mark Pettingill.  I said it before when Terry Lister resigned

when a member of parliament is elected under one banner and decides to join a different party or go independent they should resign and re-contest their seat.

Under our present broken political system some people may have voted for the individual, others voted for the party.  As an elected representative you owe it to your constituents to honor the commitment you made being elected under one party banner or another.  If you cannot honor that commitment you should immediately resign and re-contest the seat under whatever new commitment you wish to make.