The resignation of Labor MPs Josh Wilson for being a dual-citizen at the time of his nomination, and Tim Hammond for family reasons, triggered by-elections that could be held as early as July.

"We will not be distracted by Bill Shorten's duplicity and dishonesty that has resulted in a number of by-elections being required across the country around 12 months from the next Federal Election, by contesting the Fremantle and Perth by-election," the Liberals WA Twitter account tweeted on Saturday.