City of Melbourne councillor Roshena Campbell has been confirmed as the Liberal candidate for the forthcoming by-election in the marginal seat of Aston.

Federal Opposition Leader Peter Dutton attended the secret ballot, which sources say Ms Campbell easily won.

Ms Campbell, a barrister, edged out oncologist Ranjana Srivastava and former Victorian Liberal MP Catherine Burnett-Wake.

The Aston by-election was triggered by the resignation of former cabinet minister Alan Tudge earlier this month. Mr Tudge has held the seat since 2010.

Labor last week announced its candidate — former union official Mary Doyle — spurring the Liberals to ditch a planned vote of rank-and-file members to elect Mr Tudge's replacement.

Instead, the party's administrative committee selected Ms Campbell in a secret ballot, with party president Greg Mirabella seeking to avoid handing Labor an advantage in the campaign.

Ms Campbell, who is a barrister and lives in Melbourne's inner north, has promised to ease the cost of living pressures "facing so many families in the seat".

Aston sits in Melbourne's outer east and encompasses suburbs including Bayswater, Boronia and Knoxfield. 

The Liberals hold the seat by 2.8 per cent after Mr Tudge suffered a 7 per cent swing at last year's federal election.

Ms Campbell was elected a City of Melbourne councillor in November 2020 and is married to News Corporation political editor James Campbell.

The Aston by-election will take place on April 1.