Residents in Melbourne's most sought-after suburbs are the big beneficiaries of tax cuts detailed in Scott Morrison's first budget.

Prime Minister Malcolm Turnbull's harbourside electorate of Wentworth has the biggest proportion of earners who will benefit fully from income tax cuts unveiled in Tuesday's budget.

More than a third of income earners in the Prime Minister's seat will get the $315 annual relief from the government's decision to lift the threshold at which the second top tax rate applies from $80,000 to $87,000 - the largest share of the 150 electorates in federal parliament.

The Australia Institute has used income data from the last census indexed to 2015 to estimate what proportion of earners in electorates would benefit from the income tax cuts.