The change was made after negotiations between the Government and Warner Bros executives over the location of filming The Hobbit.
Ms Fenton said this would take place even if it meant losing the films offshore.
"Well who knows [if that would happen], but I don't think we should be held to ransom."
She said industry standards would only be set up if unions or employers took a case to the commission.
"Workers will not have to join a union to be part of an Industry Standard Agreement, but unions will have access to workers in the industry to talk about the standards, as they do now."
The Government said the policy was a throwback to National Awards, which for decades established pay-scales across industries and were abolished in the early 1990s.
"[Labour's] best step forward for the 21st century is a 1970s' industrial relations policy," Deputy Prime Minister Bill English said.
"This isn't just old Labour. It's real old Labour.
"It's been a long time since New Zealand had National Awards, and they were thrown out because they were too inflexible, anti-jobs, anti-growth, and difficult for businesses to be adaptable with those kinds of industrial structures."
Ms Fenton conceded that the wages bill for affected businesses would increase, but she hoped it would lead to greater investment in training and development, instead of a business model of low wages and long hours.
"We're talking about large organisations, overseas-owned, that are making quite a lot of money and sending it offshore. All we're saying is that New Zealand workers aren't getting paid enough, and they need to get a fairer share."
Unions welcomed the policy and trumpeted examples of supermarket union workers on higher pay rates than those on individual contracts.
Service and Food Workers Union national secretary John Ryall said a similar practice took place in the aged care industry.
"We have a member doing exactly the same work for one aged care employer, employed on a collective earning $2 more [an hour] than in her other job, where she is employed on a worksite with no collective."
Ms Fenton said the policy, which would lead to greater union prominence and access to non-unionised workers, could lead to stronger unions.
"But this is not about boosting union membership. It's about getting wages up."
WORK LAW
* An independent Workplace Commission to determine minimum standards, including pay, across industries where appropriate.
* Repeal the 90-day trial period for new workers.
* Repeal the change to the law around film workers that was made during the furore around The Hobbit films.
* Lift the minimum wage to $15 an hour.
* Ensuring public holidays that fall on weekends are carried forward to the following Monday.