ACT leader David Seymour swore at New Zealand First candidate Richard Prosser today and went on to criticise his weight.
Mr Seymour made the comments at a Business New Zealand conference after Mr Prosser had spoken about re-nationalising power companies.
"I realise that in a role such as mine you're supposed to have a certain amount of decorum but that makes me really angry.
"What a f**king idiot.
"I mean, seriously, you know. I mean, what an idiot.
"But that's actually the reality and that's someone who, you know, can barely manage his own diet and exercise regime and thinks that he's going to be managing a ministerial post and actually could be, we shouldn't joke about it," Mr Seymour said.
His comments came after a panel at the conference in Wellington when candidates from political parties discussed election year issues - including energy policy - with about 200 business representatives.
Mr Prosser, the New Zealand First spokesperson for state-owned enterprises, was asked by Mercury Energy general manager Tony Nagel how he would pay for a scheme nationalising the country's power companies.
"You said that you were going to nationalise or re-nationalise the electricity companies. Just a very quick calculation in my head ... that would be around $11 or $12 billion, so how are you going to fund that?"
Mr Prosser said there were ways to do it, such as long-term infrastructure bonds.
"This is not going to be 'write a cheque today and go try cash it tomorrow'. These institutions would be purchased back at whatever they were sold for and not more than that. We signalled that a couple of years ago."
Mr Prosser said infrastructure was not delivering for New Zealanders as the price of power continued to increase.
In a statement after the meeting, New Zealand First leader Winston Peters said Mr Prosser's comments about re-nationalising were not fully explained and could be considered "throwaway".
"Had he had the time he would have explained that the buyback of power companies would be at an appropriate time in the future, that is, we would only be buying back shares when they became available."