Liberal candidate Roshena Campbell says renters locked out of the property market and families rolling off fixed mortgages need more help from the federal government, promising to use a byelection in the Victorian seat of Aston to secure additional cost-of-living assistance.

A day after being handpicked by party officials and Opposition Leader Peter Dutton to run in the April 1 byelection, the barrister and City of Melbourne councillor said she would quickly move to the marginal suburban seat.