Food Safety Minister Kate Wilkinson says she will seek a review of the use of folic acid in bread - but not until a month after bakers have started adding it.

Folic acid prevents some birth defects, and the idea of putting it in bread is so women who do not know they are pregnant get the protection. Ms Wilkinson has criticised the decision to use the additive from September, which was part of a joint New Zealand-Australia food standard. However, she says that since the Labour Government signed up to it she has no option but to let the implementation go ahead.

Bakers are angry about the decision, saying it adds unreasonable costs and will not work. They say women would need to eat 11 slices of bread a day to get the required dose.

On TV One's Q&A programme, Ms Wilkinson faced criticism from Green MP Sue Kedgley, then presenter Paul Holmes, followed by all three members of the analysis panel.

Ms Kedgley said New Zealand did not have to go through with a standard - or could at least delay it - given new research had subsequently come to light showing risks. She pointed out Ireland and Britain were delaying implementation.

Holmes was upset by research that showed a possible link between folic acid use and cancer - he has previously suffered prostate cancer.

Ms Wilkinson said the research on risks was "light" and that she was legally obliged to follow through on the standard.

"We have to abide by the rules, we have to do it within the system, within the joint regulatory system, and we're doing it ...

"It doesn't set a good example if just because we don't like a decision we decide to break the law."

The influence of a feared Australian reaction to a change in New Zealand showed the country had lost part of its sovereignty, Ms Kedgley said.

Holmes pointed out cases in the past over apple exports and a last-minute canning of a single aviation market by Australia protecting its domestic interests at New Zealand's expense.

Political scientist Jon Johansson, on the panel, joined in the criticism.

"She's the Minister for Food Safety, and that means her job is to make sure that all food that we eat in this country is safe."

Another two panellists, Wanganui Mayor Michael Laws and unionist Matt McCarten, were against the proposal. Mr Laws urged Prime Minister John Key to get involved, while Mr McCarten said he expected it would be a hot issue at the next Cabinet meeting in a fortnight.

Ms Wilkinson said she would ask the Australia and NZ Food Regulation Ministerial Council meeting in Australia in October for a review. She did not know if that would be agreed to. If it went ahead, the review would take three months.

Foreign Affairs Minister Murray McCully and Mr Key had raised the issue with Australian counterparts, she said. "They don't seem to be having the same concerns that we do, no."

Folic acid is not being added to organic bread. In Australia it is being added to all wheat flour used to make bread. That was proposed here but the Greens and others argued against it.

Former Food Safety Minister Annette King said when the decision was made that it was "a triumph for humanity and common sense".

She expected the change would see four to 14 fewer neural tube defect-affected pregnancies a year, but admitted women would not get the recommended 400 microgram daily intake from bread alone.

- NZPA