Public servants will not be forced to have a 90-day probation period but it will not be ruled out in their contracts.
Labour MP Grant Robertson said government departments were being required to implement the 90-day policy by not being able to exempt staff from it.
The probation period, originally brought in for smaller companies, was extended by the Government as part of employment law changes late last year.
Labour Minister Kate Wilkinson has repeatedly said the legislation would be used only if workers and employers agreed, Mr Robertson said. "The commission has now directed state sector agencies not to contract out of or restrict any application of the 90-day law.
"Forcing it on public-sector agencies and their employers is totally against the spirit of good employment law."
A spokesman for the State Services Commission said government departments were always required to enact government policy. However, it would be silly to assume the 90-day probation period would be applied to everyone in the state sector, he said.
"You go through these incredibly long and arduous recruitment processes to get the best people, you don't then turn around to them and say: `Oh by the way, we're putting you (on a probation period),'. It's just common sense."
The commission had advised government departments not to contract out of the 90-day period, but it was up to each chief executive, the spokesman said.
"Agencies will enact government policy, but the practical side of it is that the public service chief executives are still responsible for running their business and they'll make the best decisions they can to ensure they deliver on the Government's priorities."
A spokesman for Ms Wilkinson said it was sensible for departments to have the option of using a trial period. "Any individual can negotiate the trial if they wish to and in many instances departments won't need to utilise it as they'll be employing skilled workers who are in demand."
Unions are working to have the 90-day period excluded from new collective contracts.
Public Services Association national secretary Brenda Pilott said her organisation would not advise anyone to sign up for the 90-day period and did not want to see it as part of collective contract negotiations.
Would you pay $2 to use Auckland's motorways?Related story: Auckland motorway toll could top $350 a year