The tension between the two political opponents erupted less than half an hour into the first day of annual report hearings in the Legislative Assembly.

It comes just days after the Opposition brought a motion of no confidence against Mr Barr during sittings last week, making allegations of "corruption" in the chamber which were ultimately voted down.

During a discussion on rate rises in the morning session, committee chairman Jeremy Hanson claimed that the revenue from rate rises went "into your pocket" [Mr Barr's], as Treasurer.

But Mr Barr said repeatedly that he should withdraw the assertion.

"Do we need to stop this hearing? You should withdraw that, you cannot suggest that I am personally profiting, you should withdraw that language," Mr Barr said.

But Mr Hanson said he was "not withdrawing anything", to which Mr Barr said it was unparliamentary language, repeating again that Mr Hanson should withdraw it, with Mr Hanson saying: "too bad, too bad".

"Do I have to take this outside? Do I have to take this outside, into the other chamber," Mr Barr said.

"Good practice, Mr Hanson, says that you would withdraw, or at least reflect upon that."

Labor MLA Michael Petersson then interjected, to which Mr Hanson said: "This is my committee Mr Petersson and I will make the rulings, thank you very much".

Mr Barr said he would be pursuing it, and that Mr Hanson "cannot make that assertion and leave it standing on the record", to which Mr Hanson said "good on you".

Tensions flared again later in the hearing, when debate on the City to the Lake project degenerated into "threats".

While Mr Barr responded to questions about the project, Mr Hanson interjected, to which Mr Barr said he did not "get to tell me how I answer questions".

Mr Hanson said that "I am the chair of this committee", to which Mr Barr said "For the time being, yes", before Mr Hanson responded asking "Oh, is that a threat?".

Mr Barr replied that "it is, yes", which Mr Hanson said "you're making a threat to me", to which Mr Barr said "I am, yes".

Mr Hanson asked what his threat was, to which Mr Barr said he had already "made it this morning".

"Oh, to take it outside?", Mr Hanson said.

"I will be pursuing your defamation of me this morning," Mr Barr said.

After much to-ing and fro-ing, the meeting was finally brought to some order, before a final brief stoush late in the afternoon, when Mr Barr said he would refer Mr Hanson's language to Speaker Joy Burch.

As Mr Hanson was committee chairman, Mr Barr said his only course of action was to refer it to the Speaker for a ruling on whether it was unparliamentary language or not.