ACT leader David Seymour says the government's decision to ban single use plastic bags could be killing up to 20 New Zealanders a year.
Mr Seymour said research in the US showed that people using reusable bags were susceptible to diseases such as campylobacter from chicken.
In August, the government announced it would rid the country of thin plastic bags by July next year.
Mr Seymour said the decision was made too hastily and was putting New Zealanders at risk.
He based his claims on 2013 research from George Mason University that found five people a year die in San Francisco from food-related infections such as E Coli and campylobacter after using reusable bags contaminated with the disease.
San Francisco banned non-compostable bags in 2007.
The research concluded that any health costs associated with the ban of plastic bags in San Fransisco swamped any savings from reduced litter.
Mr Seymour admitted plastic waste filling the oceans was a concern, but said the blame for that should lie with African and Asian countries, not New Zealand.
"The problem of New Zealanders letting go of their plastic shopping bags and them ending up in the ocean is a problem but an absolutely tiny one.
"It's not a problem that justifies the level of inconvenience and potential public health danger that comes from a ban on plastic bags," he said.
Mr Seymour said people would be particularly at risk heading into barbeque season, carrying their chicken in reusable bags in warm cars.