New South Wales Premier Barry O'Farrell will likely fire state Finance Minister Greg Pearce over suspicions he has been using public funds for his private travel. The threat came after Mr O'Farrell warned Mr Pearce of his drunk behaviour in the state parliament last week.

On Thursday, the minister needed to be assisted from the parliament during the discussion on victims' compensation legislation because of his drunken state.

The next day, Mr Pearce went on sick leave, but actually went to Canberra to attend a drinks function at the launch of a lobbying firm.

He allegedly charged the trip to state coffers, on top of stating that he went to Canberra to visit a housing development project, paving the way for the premier to consider removing him over a possible breach of ministerial travel guidelines.

Mr Pearce later said the trip was a private once and paid for the travel cost out of his pocket, but it may be too late because the premier had already ordered Chris Eccles, director-general of the Department of Premier and Cabinet, to investigate the minister.