Labour leader Andrew Little says "there won't be any new onerous obligation" for employers in his plans to modify 90-day trial periods for employees.

Andrew Little appears to have made an about turn on labour law reform, ruling out abolishing the 90-day trial period for workers.

The Council of Trade Unions (CTU) has called on Labour to clarify its position and the Government is accusing Little of "weasel words".

At a breakfast in Upper Hutt on Friday, Little was asked about Labour's position on 90 day trial period, in which employers can dismiss workers.

"Our policy is to add a fairness requirement," Little said.

The question frequently came up from employers, Little said, with every employer indicating they already gave feedback to any worker they let go, so they would not be affected under Labour's policy.

"We just want to make a requirement to give feedback so the person knows whether they're on track to make the grade or not."

Asked afterwards if that meant that the trial periods would certainly stay, Little said: "Well we wouldn't be talking about making the 90 day trial periods fairer if we were going to get rid of it."

Any changes would not have a significant impact on employers, Little said.

"There won't be any new onerous obligations in that regard, but it will make it fairer and we will write that into law."

While he was that party's labour spokesman, Little promised to abolish the trials, which have been popular with many employers but are opposed by unions.

"We don't need the 90-day law and under Labour it will go," Little said in a statement in June 2014.

As recently at his state of the nation speech in January, Little refused to discuss the party's position on the trials.

CTU president Helen Kelly called for clarification.

"Making it fairer gets rid of it, right? He needs to clarify that," Kelly said.

"We would expect them to effectively get rid of them by making unfair dismissals unlawful."

Kelly said the 90-day trial periods allowed workers to be dismissed for reasons which would otherwise not be fair, without giving the worker the option of taking a personal grievance claim.

If Labour introduced "just cause" provisions to the trials to allow personal grievances, the CTU could accept that, as this returned to the earlier rules in existing laws covering probationary periods.

"But if what they're saying is modifying [the trials] to simply allow unfair dismissal, but you've got to give reasons, then that certainly, as far as I'm aware, is totally against their [Labour's] position in the past and would be unacceptable to us, totally unacceptable," Kelly said.

Economic Development Minister Steven Joyce said the statement from Little was "weasel words", designed to please the audience he was speaking to.

"He's sort of saying there won't be change and yet there will be change...He doesn't know which way he wants to go and I suspect he's saying different things to different audiences," Joyce said.

"Small business owners will be looking very carefully at the fine print of any proposed changes because actually they think it's working well the way it is. They like the 90-day trial as a way of bringing on new people that they may not be 100 per cent confident about but they want to give them a go."