Victorian state Liberal MP Ryan Smith resigns, sparking by-election in Melbourne's north-east

Liberal MP Ryan Smith cited the "growing negative tone of politics" in his decision to resign. (AAP: Joel Carrett)

Voters in Melbourne's north-east will head to the polls for the third time in just over a year, after Liberal MP Ryan Smith — a critic of leader John Pesutto — called time on his Victorian political career.

Mr Smith will resign on July 7 to take up a job in the corporate sector, forcing a by-election in Warrandyte.