The Coalition has harnessed three grant programs worth up to $700 million as political campaign tools, sidelining local MPs and having unelected candidates hand out grants worth hundreds of thousands of dollars to local facilities in marginal seats.

Independent Cathy McGowan has become the latest MP to refer the conduct to the Auditor-General, as new advertising campaigns paint taxpayer-funded Sport Community Infrastructure grants and the Building Better Regions Fund as Nationals Party cash.

The campaigns, complete with party branding and appearances by candidates in marginal seats, are expanding a month before the election campaign is formally due to get under way.

Nationals deputy leader Bridget McKenzie. Credit:Dion Georgopoulos

A Sydney Morning Herald and The Age analysis of pork-barrelling by both Labor and Coalition governments showed voters in marginal seats collected tens of millions of dollars more than those in safe electorates over the past decade.