Prime Minister John Key is signalling changes to industrial relations laws, but is keeping tight-lipped about the details.
The move comes after a raft of employment law changes, effective from April, were met with strong criticism from unions and opposition parties.
The changes included an extension to all employers of the 90-day trial period for new workers.
Mr Key today said it was too early to detail further changes.
"All I can tell you is that it's likely National will go into the 2011 campaign with a couple of initiatives around industrial relations, but what those are it's too early for us to tell," he told reporters.
Mr Key said it was not his expectation that the current trial period would be lengthened beyond 90 days.
Green Party co-leader Russel Norman said he would be concerned if any changes undermined the ability of unions to bargain collectively.
The only alternative to collective bargaining was private organisations that tended to side with the employer, he said.
"We think that we need free unions in a democratic country, and if we undermine free unionism then I think we've got a real problem."
Council of Trade Unions secretary Peter Conway said the Government should spell out the further changes so voters had a clear indication of what was being proposed.
"Every change enacted so far has made things tougher for workers when things were already tough from the recession," he said.
"We have already seen a raft of changes including removal of appeal rights against unfair dismissal, restrictions on union access to workplaces and making the fourth week of annual leave tradable for cash."