Key Labor figure Paul Howes has lashed out crudely at Labor MPs he says are undermining Prime Minister Julia Gillard, telling those who anonymously attack their leader to "grow a pair".
The Australian Workers' Union national secretary, who earlier in the week pledged his 110 per cent support for Ms Gillard, took aim at insiders who spoke anonymously to journalists and speculated about a return to Kevin Rudd or spread criticism.
"Nothing upsets me more lately than opening newspapers on a daily or weekly basis and reading anonymous quotes from 'senior Labor sources' undermining our Prime Minister, undermining the leadership of our movement and this country," he said in his closing speech to the AWU national conference on the Gold Coast.
"What a bunch of gutless pricks they are that they can't put their names to what they are saying."
The tough talking drew applause from union delegates at the four-day national conference.
Mr Howes appeared on Lateline the night before Ms Gillard was installed as Prime Minister in June 2010 to declare that the powerful AWU had withdrawn its support for Mr Rudd.
Mr Howes told the gathering: "I might get the odd attack for appearing once or twice too many times on television or being a bit too blunt about [former Rio Tinto chief] Tom Albanese or former prime ministers or going on shows like Lateline on that particular night and maybe that's right, but we say what we do, we have the guts to put our names to what we mean, we don't background.
"We get out on the front foot and we say it loudly and clearly."
Mr Howes said he had a message for Labor members who were trying to undermine the cause.
"Grow a pair and put your name to what you're saying and have the fight out here publicly. Don't go slinking around the back rooms of the press gallery on a daily basis. Come out and articulate your case. Make your message. Have the discussion with the Australian people. Get out there and argue your point."
The warning came after Mr Howes warned that unionists faced "the fight of their lives" to prevent the election of an "extreme" Tony Abbott-led government.
Mr Howes launched a full-throttle attack on Mr Abbott as he reaffirmed plans to send advocates into key marginal electorates to promote the struggling Gillard government.
The move ties into a broader union movement strategy to use word of mouth in the workplace in an attempt to turn the electoral tide in the face of opinion polls pointing to a landslide Labor defeat.
As the four-day AWU conference wrapped up on Thursday, hundreds of delegates signed a pledge vowing to "stop Tony Abbott in his tracks".
Mr Howes took up the attack to Opposition Leader Tony Abbott and some of his frontbenchers.
"We know what type of man Tony Abbott is. We know what type of man Eric Abetz is. We know what kind of joker Joe Hockey is. Hell, we even know who Barnaby Joyce is even if he doesn't know it himself."
Mr Howes ridiculed the image of Senator Joyce as an average Australian, saying: "He's a guy who goes on cruise ship holidays with Gina Rinehart. He's a guy who writes letters to Gina Rinehart's children begging them to stop litigation against their mother."
Mr Howes labelled Mr Abbott as "the most inconsistent so-called conviction politician that this nation has ever seen", pointing to contradictory statements over climate change and WorkChoices.
He said Mr Abbott was only consistent on "extreme social conservative" positions on reproductive rights.
"It's hard to actually call Tony Abbott a conservative because he's so extreme; because he's so brash; because he resorts to the politics of smear and innuendo so much. That's not conservative; that's extreme. And when nations have extremist politicians and when extremists gain power it's a very very scary thing."
But after launching the attacks, Mr Howes bemoaned how politics had become "so nasty, so personal".
"I do despair sometimes at the level of political discourse in this country," he said.
Mr Howes later denied he was being hypocritical, saying: "I'm not in Parliament ... I think it's right to call a spade a spade."