A dormant shell company which has been flagged for deregistration by Australia's corporate regulator is being used to fuel new attacks on Victorian Liberal Senate front runner Greg Mirabella.

The Wangaratta-based farmer is set to come under fire over his links to the company, Global Enviro Pty Ltd, as the party's contest to replace former communications minister Mitch Fifield threatens to be overrun by bitter factional feuding and "mud slinging" ahead of next Saturday's preselection.

Greg Mirabella, husband of former Liberal MP Sophie, is a front-runner for a Victorian Senate vacancy. Credit:Matthew Smithwick/ Border Mail

Mr Mirabella and Sarah Henderson, the former federal MP for Corangamite, have emerged as the two frontrunners in the "neck-and-neck" race for the casual vacancy after Mr Fifield resigned from Parliament last month after his appointment as Australia's next ambassador to the United Nations.

Mr Mirabella's factional enemies, who are said to be growing "increasingly desperate", have seized on revelations the Australian Securities and Investments Commission has begin strike-off action against the company, of which he is a director and minority shareholder.