Liberal National Party Senator Barnaby Joyce has slammed the Greens' endorsement of the Whitehaven Coal hoax and criticised the prime minister for staying silent on the issue.
Senator Joyce says it was wrong for Greens Leader Christine Milne to endorse an anti-coal mining activist's scam that wiped millions from the coal miner's share price.
"That is not a noble action of an environmental warrior," he told reporters in Brisbane on Thursday.
"That is the action of a person who's lied and defrauded people out of their money."
Having strong views against coal mining did not justify telling a lie, he said.
"You can't go out tomorrow and just say, well, to remove the Greens from the political scene I'll say that (Greens Senator) Lee Rhiannon is marrying a whale farmer.
"It would be a lie and it would be the wrong thing to do."
Senator Joyce added that given the government's relationship with the Greens, Prime Minister Julia Gillard should not remain silent about the hoax.
"The prime minister is sitting back, silently, just accepting the fact that she's in business with a party that a couple of weeks ago said they'd changed their ways and today are back out endorsing lies," he said.
Earlier this week, Senator Milne reportedly described activist Jonathan Moylan's hoax as being part of a proud tradition of civil disobedience to highlight wrongdoing.
Mr Moylan, a member of Frontline Action on Coal, sent a fake press release to media outlets claiming the ANZ Bank had pulled its $1.2 billion loan to Whitehaven Coal.
The anti-coal mining group accuses Whitehaven of planning to destroy a koala habitat and force farmers off their land near its Maules Creek project in NSW.