Workplace Relations Minister Iain Lees-Galloway claims three of the four main points of a campaign against proposed labour law reform are factually inaccurate.

The minister leading labour law reform has accused leading employer groups of running a deliberately misleading scare campaign, contributing to a plunge in business confidence.

BusinessNZ's regional member groups have been running media campaigns claiming the Employment Relations Bill would slow business growth and make it difficult for employers to engage and develop staff.

In some cases the groups - which include the Otago, Canterbury and Wellington chambers of commerce and the Auckland-based Employers' and Manufacturers' Association (EMA) - have blamed the proposed changes for the slump in business confidence since the 2017 election.

DAVID WHITE/STUFF Wellington Chamber of Commerce chief executive John Milford said the slump in business confidence would not improve if the government pushes ahead with proposed changes to industrial legislation.

Wellington Chamber of Commerce chief executive John Milford said the slump in business confidence "is not going to improve as long as [the Government insists] on pushing ahead with their proposed changes to industrial legislation".

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Leading surveys have business confidence at the lowest level since the 2011 Christchurch earthquake.

SUPPLIED Canterbury Employers Chamber of Commerce chief executive Leeann Watson said proposed changes hurt employers' flexibility.

Workplace Relations Minister Iain Lees-Galloway said the employer campaign was "disproportionate" and was creating unnecessary concern.

"It would be helpful if they could be proportionate in the debate, about what the Government is doing, and also factual as well."

Lees-Galloway claims three of the four central points raised by the campaign were "factually incorrect" and he was writing to businesses which had raised the campaign with him.

"I think that's been deliberate by the EMA, they've been misleading their members, and the rhetoric that they've been using and the National Party have been using has probably contributed to the fall in business confidence itself.

"They've been misrepresenting what our changes actually mean and in some cases fearmongering and I think that's unhelpful."

The "fix the bill" campaign has warned that the proposed bill would end 90-day trials for companies with at least 20 staff, will give union officials access to the workplace at all time, will force businesses to settle collective agreements and will remove the right to opt out of multi employer collective agreements.

In letters being sent to people who have written to him in response to the campaign, Lees-Galloway says the law did not allow unfettered union access and that businesses do not have to settle collective agreements or sign up to multi-employer agreements where there were reasonable grounds not to do so.

Lees-Galloway agreed the 90-day trials would end for businesses with 20 or more staff, but said the only serious analysis of the trials showed they "don't create jobs in the first place".

Many businesses he had spoken to did not necessarily agree with the legislation but were comfortable with it, recognising that most of the settings were in place during the previous Labour Government.

"They're policies most businesses should recognise and they're policies that were in place during a period when we had sustained growth, where we had low unemployment," Lees-Galloway said.

Leeann Watson, chief executive of the Canterbury Employers' Chamber of Commerce, said the employment law campaign was drawn from the interpretation of the proposed legislation from the business community. If what Lees-Galloway was suggesting was correct then he appeared to be building a case to not change the law.

"There are plenty of opportunities to do what they're suggesting under the current regime. [The proposed changes are] putting more compulsion in it and hurting flexibility for employers."

Lees-Galloway's claim around 90-day trials was "disingenuous", Watson said, because the trials were never about creating new jobs, but about allowing employers to take a chance hiring someone who they might not have otherwise considered.

Watson dismissed the claim that the organisations would contribute to a fall in business confidence as such a move could threaten their position.

"We rely on businesses as members to support the viability of our organisations. A drop in business confidence is not only a concern for the economy, but also for us as organisations."