Long-serving minister Paul Papalia has announced his resignation from politics, triggering a cabinet shakeup and a byelection in the southern Perth seat of Secret Harbour.

Paul Papalia’s resignation will trigger what is expected to be a highly contested byelection in his southern suburbs electorate of Secret Harbour.

State minister Paul Papalia has resigned from politics after almost 20 years, and Labor fears his once-safe seat could fall to One Nation.