Labor's point man on the public service, Brendan O'Connor, says the federal government would reap a nasty harvest if public servants were poorly treated during bargaining negotiations.
The man who held seven ministerial positions at various time under Kevin Rudd and Julia Gillard has offered some advice to Coalition Senator Eric Abetz, now overseeing collective bargaining affecting 160,000 public servants across 117 agreements.
"What we don't need is an anxious disgruntled public service, who feel they've been badly treated, going on indefinitely because that's not going to be good for them or the government," Mr O'Connor said.
The opposition's employment and workplace relations spokesman said the federal government was in a difficult position.
"You've got a government that has to have enterprise agreements and doesn't like enterprise agreements but hasn't got the courage to repeal them and most Australians do like collective agreements."
He pointed out a change in the bargaining playing field: the en-masse expiry of agreements across the federal bureaucracy, most of which happened last month, allowed a trigger for lawful industrial action under the Fair Work Act.
"That's just something for Eric to contemplate when he's working out how he's going to get a settlement," he said, adding the Coalition was trying to "cower" public servants into not accepting pay rises.
"I'm always skeptical about the Coalition government to act in good faith when it comes to industrial relations - it's not in their DNA.
Mr O'Connor, 52, has more time on his hands compared with his days running the Immigration portfolio when he could knock back appearances on high-rating current affairs programs a few times a week.
The former union official looks at public service matters for Labor along with shadow special minister of state, Gary Gray.
"For the life of me I don't know how Minister Abetz is going to handle it," Mr O'Connor said.
"Eric doesn't strike me as someone great at accommodating other people's points of view on industrial relations.
Mr O'Connor predicted the Coalition would cut too deep and be forced, like the Howard government, to increase numbers again in the future when it realised it could not function properly without the correctly-sized workforce.
He said his party's position on performance pay for public servants had not changed - it was still cynical on the matter.
"The bonus can be used too readily in the wrong hands as a stick to punish candour and fearless advice," he said.
He said skills, responsibility and perhaps experience could be measured to guide salary.
"Rather than, 'you did a job for us so we'll give you a bit of money'," he said.
"The flip side is 'we don't like how you said that in Senate Estimates so we're going to hurt you'.
"No one's ever going to admit they'll withdraw money but it's open to abuse if you have the minister having such powers over public servants who, remember, have to remain independent."
Mr O'Connor said secretaries were already well paid.
"The secretary who reported to me (when he was in government) was paid twice as much as me and probably had a less precarious job, didn't have to front the media."