The Diaz family looks set to cement their dominance over Sydney's north-west as their main political rival appears to have lost a messy battle for control of the state's largest Liberal party branch.

The career of Kevin Conolly, the MP for Riverstone, is under threat after the NSW Liberal Party executive decreed that all party branches have until the end of the year to hold an annual general meeting, or be forcibly dissolved.

Election day: Riverstone MP Kevin Conolly at the Quakers Hill East Public school polling station in August. Credit:Geoff Jones

It may seem a small order, but the branch containing most of Mr Conolly's supporters has not met this year following a very public and bitter falling out between Mr Conolly and Jess Diaz, patriarch of the powerful political family and a Blacktown councillor.