Union bosses are going toe-to-toe with the Labour leadership today as they fight for delegates at the Labour conference to approve a motion opposing the party's support for a public sector pay freeze.
The motion is the climax of an increasingly brutal war of words between GMB leader Paul Kenny, Unite leader Ken McCluskey and shadow chancellor Ed Balls.
In a line David Cameron would probably sympathise with, Kenny said Balls would "give an aspirin a headache" and prepared to unveil a dossier of 'Balls-ups' during the shadow chancellor's time in the Treasury.
"We must be upfront with the British people that under Labour there would have been cuts and that – on spending, pay and pensions – there will be difficult decisions in the future from which we will not flinch," Balls said in his conference speech today.
"Before the next election – when we know the circumstances we will face – we will set out for our manifesto tough new fiscal rules to get our country's current budget back to balance and national debt on a downward path.
"Our fiscal rules will be monitored, independently, by the Office for Budget Responsibility. When we sell off the government's shares in the banks every penny will go to repay the national debt."
Balls seemed to be savouring the row with union bosses during a round of media interviews.
"If people see some trade union leaders having a go at me because I am saying we have got to be disciplined on spending, tough on pay, I think most people would say that's what we'd expect from the Labour leadership and that's what we are going to deliver," Ballls said.
Since Tony Blair's time in opposition, pollsters have noted that voters respond well to front benchers having a row with their own party.
Some believe the reason most polls find Cameron to be more capable of tough decisions than Ed Miliband is because the Labour leader avoids public rows with unions and his own members.
Balls, who is rumoured to have increasingly tense and difficult relations with Miliband, clearly had no such hesitation.
"It's not my job as shadow chancellor to make everybody happy," he said.
"My job is to make sure that we've got strong, credible policies which add up and make sense and are costed"
Unite leader Ken McCluskey proved a more dangerous opponent than Balls may have bargained for, when he won a standing ovation from a mostly positive conference.
The union leader said the previous Labour government put "too much faith" in the City and demanded the shadow Cabinet "come out of the shadows and be heard".